OK-----I need some help...

I'm restoring a VP-1. Have it basically finished (just need to install "new" engine and prop, make cowling and take to hangar....).

Decided to temporarily mount the engine and do a preliminary W&B to see where the empty CG falls as of now........got some interesting results.

Using the front face of the firewall as the Datum...main gear is at 23.8125", tailwheel at 187.875". Leveled the plane and got 48.0 lbs on TW, 235 lb Rt main and 226 lb Left Main. (discrepancy in rt and lt---not sure our leveling dude got the side-to-side level exactly right----for and aft much easier to assure correct!)

I got an empty CG of 39.3"------?? The acceptable CG range in flight is 31 to 39", best CG empty is 30-32". The only variable weights are the Fuel (8 gal at 14") and the pilot at 44. These #s just don't work out..........

So----how do I calculate the distance to move the engine forward to place the empty CG at the forward limit of acceptable range--ie, 31"?? (Engine is 180-186 lbs depending on adding the starter or not----at (-)10.5" without starter and (-)9.75" with--starter moves the CG of the engine itself 1.25 inches aft)

I've just not been able to make the math work......

Here's what we have:

Rt Main --- 235 lbs x 23.8125" = 5596 moment
Lt Main --- 226 lbs x 23.8125" = 5382 moment
TW --- 48 lb x 187.875" = 9018 moment

Total wt = 509 lbs
Total Moment = 19996
Empty CG 39.3"

Best Empty CG range 30-32"
Allowable in flight CG range 31-39"

Engine wt (as weighed in above calc) 180 lbs at (-)10.5"

* Will have a small battery to play with to fine tune CG (for ignition and starter if used)--weight/location are undetermined at this time.

Is there an equation that I just haven't found to help with moving the engine and doing the calculated change?

Help!!