good point, stainless, I reviewed the video of the dyno pull and the engine moves about 3/4 of an inch. So as an estimate of this effect on the chasis, hypothetically, If I could measure the force it would take to move the engine this distance I would have the total moment of inertia. Would one then assume that this force would be spread between, the whole right side of the chasis. Watching the dyno pull at max rpm and seeing the engine torque at max rpm was pretty convincing that one should somehow acount for this weight transfer at max speed.
So this goes back to my original question, how close is close enough.