"1.5" gals? I thought you said 4 gallons. 1.5 in a two stroke isn't great range.
Shorter wheelbase with more power more suddenly...hmmmmm not my cup of tea
That's one low seat height..is it for real?
Setting sag is going to be critical...short wheelbase, travel almost the same as ground clearance.
Everything is going to depend on rideability of the motor, it's smoothness and transition to the pipe.
Assuming 2 lbs for fork/shock weight...
Assuming 4 lbs for radiator fluid weight..
Assuming 4 lbs for tranny fluid weight.
Assuming 28 lbs for 4 gallons of gas.
A 1.5 gallon gas takes makes sense.
I had a BSA500MX for two races with my cast on, it had a 1.5 gallon aluminum gas tank, and it sure made the tall four stroke motor seem not so bad in the corners.
In my day, big bore and short stroke typically meant pipey motors, or at least really quick revving engines, rather than torque and tractible.