I am finishing up a Sig Morresey Bravo i bought 90% complete.
The throw on the ailerons as per plan are 1 1/8 down 1 1/4 up

The Builder through design will allow about 7/8 down and about 1 inch up.
Should I fly it this way.

Wont be a major thing to disassemble and fix
.
If im not happy with the performance then disassemble and fix

I'd recommend you last statement. Fly it, then decide.

Ditto. I have built at least 20 kits in my day.

I agree, finish it up and fly it. If you need more authority try mixing in a bit of rudder with the ailerons before performing major modifications. On many planes a little rudder helps a lot!