GT 5000 PTO problem

I have a Craftsman GT5000, with a 27hp Briggs. I finally got the carburetor fixed and it's running awesome. When it was running bad, and I engaged the PTO, it would bog it down, until it died. Except for one time. I stayed running. Sluggish, but still ran the blades. So with the newer carburetor, I've got all the power I thought I needed.
But now, when I engage the PTO, even at the highest RPM's, it still bogs down the mower.

IMPORTANT: The PTO engages, and the blades spin for the 2 seconds it takes for the engine to bog down? Push the button in, and it fires right up.
I've read some about this, and some have had trouble with the seat safety switch. I had to by pass mine, because the new seat (off a different mower) didn't have the same type/size/shape of switch. Therefore, the one that came with the mower, would no longer fit.
If the mower cranks, with the seat switch bypassed, is there another part of a safety switch that needs to be jumped too?

The switch is a four in a row connection. Not two on top of two.

Or am I barking up the wrong tree with the safety switch?

P.S. This mower is one I'm keeping for myself. So I personally don't even have to have a safety switch.

GT 5000 PTO problem