Starship Combat near Planets

I've done a few "back of the envelope" engineering calculations,
trying to figure out a consistent time/distance scale for Full Thrust
(and other games, which is why I've cross-posted, something I do
about every alternate leap year).

Anyway, my initial thoughts were:

If we get within a factor of 2, that's near enough.
It's gotta look good - be compatible with available models, tables.
It's gotta feel right - turn lengths, weapon distances, speeds must be
plausible.

For the purposes of getting something about right, I didn't sweat the small
stuff. Thus:

Pi = 3 3 x 3 = 10 10.8 = 10 1.414 = 1

For all intents and purposes.

This is what I got as some reasonable values: 1 MU (Movement Unit) = 1"
there may well be some arithmetic mistakes in the below - feel free to
check them out. But I think they're OK within an oredr of magnitude.

System 1a

1MU = 1000 km (1/300 LightSecond)
Earth-type Planetary Size about 6MU diameter - so a Floral Ball will do.
The moon would be about the size of a tennis ball. Lunar Orbit 400 MU away (so
double planets should have about 10 meters between them).
GeoSynch Orbit about 48MU away - fits on a table tennis table - just.
At GeoSync, speed is 1MU in a circular orbit. 1 move = 5 minutes (300 secs) 1
Thrust = 1 g
c is approx speed 100,000, or 300 MU/sec
1 MU/turn = 12,000 km/h

1b 1 move = 30 secs 1 Thrust = 100g c is approx 10,000
1MU/turn = 120,000 km/h

1c 1 move = 3 secs 1 Thust = 10,000g c is approx 1,000
1 MU/turn = 1,200,000 km/h

1d 1 Thrust = 2g 1 move = 100 secs c is approx 30,000

Consistent Time/Distance Scale #2

1 MU = 10,000 km (1/30 light sec)
Planetary Size about 0.6MU - so a large marble will do.
Lunar Orbit 40 MU away
Moon size - ball bearing.
GeoSync - about 5" away
1 move = 15 minutes 1 Thrust = 1 g c is approx speed 10,000

Any of the above would be fine, though I myself like System 1, so the planets
look reasonably planety.

That lead me to think about Kinetic Energy weapons - K guns in FT terms.
K-guns in system 1:
* Travel at 0.001c
* Weigh 1 kg each (small - about the size of a baseball, if made of
something like metal)
*Accelerate over 1/10,000 sec and over a distance of 150 metres, at 3
billion g.

They'd take 10 secs to reach maximum range. They have a kick that would
accelerate an aircraft carrier to full speed in
1/10,000 of a second.
Get received like a 100 tonne mass going "faster than a speeding bullet"
-
so imagine getting hit not by the shell a tank fires, but the tank itself at
the same hypersonic velocity.
Or alternatively, like a 1000 tonne mass going from 120 km/h (75mph) to
dead
stop in a distance of 1.5mm (1/16")

10t hitting at 12,000 km/h
100t at 3300 km/h
1000t at 1,200 km/h
100,000t at 120 km/h