Mulling some stuff.

1) Jump is precise: the canonical variation of a day or so MUST be something that the navigator knows ahead of time, as part of calculating the jump, because that space of a day will mean that the target system's star, planets, everything will have moved. If the canonical ability to jump within 100 diameters of a specific planetary body is correct (as well as other canonical references, like the HG allusion to coming out of Jump with black globes on to sneak beyond and surprise an enemy fleet) then the duration of a jump MUST be a known factor. It needn't be known until calculation of the jump is complete, but it will be known afterwards.

2) It's been established that jump masking is a thing that happens. That means that solar diameters, GG diameters all make a difference. Needn't figure that stuff out for every system, but for some? It would be a good idea.

EDIT: Setting up whole systems via Book 6 has been annoying, persnickety, and revelatory. It's cool: adds some real "geography" to space that'll be fun to play out. If you go to the trouble of figuring out orbital periods and calculating the changing distances between planets and satellites, it gets even better: In the space of weeks, the relationships between every body in a system might change, with effects on politics, trade, everything. It's cool.

3) I really ought to figure out a way to rough out typical relative velocities for starship encounters if I'm going to continue putting up with vector combat. If one goes with High Guard, that's not so necessary:

EDIT: Keeping this simple. A simple encounter:
a) set location of ship A, choose direction of ship's destination and determine distance from it (for ex, 640000km from mainworld)
b) choose range and bearing of ship B (appearing at detection range, direction 1-6 from ship A)
c) choose relative vector of ship B (1-6+ vector, direction 1-6)

Begin play.

4) If you're putting out a distress call, how soon can one expect help? One model I toyed with is this: each turn of combat, roll 2d against planetary population, with a modifier for starport type: if the result is population or lower, there's a response and help is on the way - in 1-6 turns. (Is that too soon to hope for? Maybe it matters where in the system the encounter takes place?) On the turn help arrives, it shows up in the reserve: on subsequent turns, the assisting ship can take the line.
EDIT: So far this seems to work for me.

Hit Or Missile II

So, generally when I'm playing vector combat, it's using the Mayday board - but at Book 2 scales and book 2 damage rules. (each hex 10000k, each turn 1000 seconds, 1G results in 1 hex vector change.) The book 2 and SS3 movement rules don't precisely match, partially because of how the hexes, er, quantize the movement. 

Maybe a happy medium for Mayday would be this:

Continuous burn: Uses max fuel until fuel is gone. Course changes permitted.
So 6G6 accelerates once at 6G then coasts; 3G6 accelerates twice at 3G with a course change in the middle.

Limited burn: Can be set from lowest to highest g, will use that acceleration until fuel expended. Course changes permitted but acceleration remains constant.
So Limited burn 3G6 can go 1G 6 times, or 2G 3 times, or 3G twice; but it can't switch up or coast between burns

Discretionary burn: Can do whatever until fuel is gone: 6G6 might go 1 G1 burn, then a 5G burn, with a coast period between, or a 3G burn with 3 1G corrections thereafter. That would make the 6G12 make sense.

Need to experiment with this more. 

Now, in SS3/Book 2, missiles that intercept the target (within 25mm, or 2500 km) are assumed to home in and impact with the target, possibly doing kinetic damage above and beyond the dice for the basic explosion.

If I recall correctly, in order to intercept in Mayday, the missile's "present position" has to end up sharing a hex with the "present position" of the target. Crossing over isn't enough. So there's no real benefit to having a continuous burn missile with a high G, you'll just overshoot your target. That's pretty likely even with a continuous burn of 1G. 

A thought:
Perhaps this is a good place to insert a player-character, in mayday-style missile combat. If a missile's vector intersects with - but does not end in - a target's hex, then the gunner's skill can be applied to adjust the missile vector to achieve the intercept.

Either shorten the intersecting vector by a number up to the gunner's skill
OR
roll 8+ to intercept, minus the number of hexes overshot, plus gunner skill.

How does that play?

Hit and Missile

Dancing around with Book 2 and Mayday, again, and remembering why I switched to High Guard.

I love the idea of vector movement, even in hex format.

It's just that GDW never really sorted out a good, simple missile rule for it. The Special Supplement on missiles added complexity, contradictions and typos instead.

High Guard abstracts EVERYTHING, to be sure, but it does so in a way that a) you don't need to take over a whole table or floor to map out a simple fight and b) it does, definitely make basic combat a simple matter - including the possibility of escape and avoidance in many cases.

So I don't know. Talking with the boys on COTI about it.

***

One thing I'm definitely inclined to do, should I revert to High Guard for battles, is keep track of missile expenditure. In small fights, that's more than possible. It makes sense in all sorts of ways.