Good point. If your reading the "lift at pin" weight you wont even get that capacity with a bucket and def not with a set of pallet forks.Keep in mind that the CG of the load on a pallet will be a couple feet out from the pins, and thus the capacity will be less as the lever arm is longer.
SSQA pallet forks weigh about 250 lbs. The 7800 probably does not have SSQA though. Forks that clamp on the bucket will have significantly less capacity than SSQA forks as they will place the load CG even farther from the pins.
If your forks are 48in long you have to assume your load is 24in from the pin at minimum. Il be willing to bet you will struggle to lift 800lbs...not including any tractor tipping issues.