I would use the fuel tank of an LTD / CSR.
It fits to the B-frame with only minor adjustments at the rear, middle holder / pin.
Either enlarge the hole to a slot in the frame or reduce the size of the pin at the fuel tank.
Can be secured by a small hole in that pin and a cotter pin through it. Large washer in between.
It has small capacity (10,6 liters) so it has low weight.
It has a drop shape and you can lean forward as much as you like.
All the “top fuel sprint bikes” at Glemseck are long and very low, so clip-ons are unavoidable.
… if there is a risk of doing a wheelie right off the starting line, it may be tricky to handle that with clip-ons. I would go for a narrow superbike bar, which improves the “handling” in that critical situation.
It supports a relaxed sitting position as well and that might be an advantage during waiting periods.
It also avoids the “lean your head way back” position, just to be able to look horizontal.
I think a relaxed position with much space to move the body is more worth than some theoretical advantages in weight distribution of a permanent stretched position with clip-ons.
BTW: I am riding Z750Twins since nearly 25 years now and I have never done or had the tendency for a wheelie. In typical situations it always comes to rear wheel spin.
Sprinting with the tuned engine and whatever transmission ratio, I expect that rear spin to appear and the steering bar and the handling of it must cope with that situation.