Take it like a true all out Street race. He's got a bigger motor, bigger tire, etc. He may not run the number, but will probably either get hurt, hurt some thing or hurt your wallet if he tries hard enough.
He's got to give some thing up. No heros or egos here, beg till he gives you the comfort zone spot, then run him again for the real coin.
I would have said to get the run off the very next day at a track so that he has no test and tune set time, but what ever its worth, go get 'em with no fear.
Hope he or a friend/s are not spying on this board to see what your blueprint for a race is forming up top be.
You have the smaller cube and old school suspension, so he should give a spot being that it is a featherweight as well.