I'd probably go through the ALR "Virtual Museum" looking for squirrel guns and see if there was one there that really struck my fancy and swayed me towards one ignition system or another.
If my math is right, for the straight barrel you have, a halfstock may offer a weight and balance advantage. A 42" barrel in 13/16 width ought to weigh about 87 oz, so the whole gun, lock stock and barrel, ought to weigh in at about maybe 7-1/2 to 8 lbs in fullstock flint. A 36" halfstock is going to have about 70 oz of weight in the barrel, a little less wood, so maybe 6-1/2 lbs of weight total?
I have a fullstock 36 flinter, Southern mountain style, with a 44" swamped barrel - it only weighs 6-1/2lbs. Part of the reason I bought it was that it was representative of the region some of my ancestors lived in, they would have been familiar with and used similar guns, so in a sense I was shootin' jes' like great-great-granddaddy used to. If my ancestors had been from Ohio (there but by the grace of God...) I might have leaned more towards one of them pretty little Vincent percussion guns.
Good luck, and happy building. SCL