I made an expensive mistake

Do you have a spare fuse location, you could parallel two 20A fuses to run the slide in a pinch.
 Sort of like WFCO did to provide reverse protection with two paralleled 40A fuses.
  You could even try 2 paralleled 15A fuses but they usually don't balance exactly so they may blow if it really draws 30.

Interesting that the Charge Wizard button is on the fuse board, on the one I did it was a wired remote, which I like better anyway since you can mount the remote in a convenient spot to work it and be able to see the status LED. 

It would be very easy. You would need to get a 30AMP relay, most automotive stores would have one, and a inline 30AMP inline fuse.

Wire the normally open contacts on the relay through the 30AMP in line fuse from the battery and to the slide wire. Wire the relay's coil to the 20AMP (or smaller) on the panel.



Instead of the fuel pump the load would be the slide, 30. 86 would be from the out put of the panel.  85 would be ground. Everything should work like normal.

Well, I'd hate to see you give up on the PD; it's just a so much better unit. The ideas from Cap-n-Cray and Budward are good, but a bit complicated for you. The relay requires some smarts and work; the parallel fuse idea is conceptually easy but requires tricks to make them share equally. I don't think you'd have trouble with even a 30A fuse on the board. There is very little in that circuit on the board, but they have to put some limit on it. Is there any trouble getting the #10 wire into the screw terminal? BTW, the troubleshooting guide on my Schwintek slide unit recommends a 30A fuse too, but LL fused it at 15A in the PD converter and it works great. 

If you split the power like Budward suggested. It would be better to have two wires from the panel and wire nut them together with the 10 gauge slide out wire.

I would hate to over load the new PD, but it should be protected by the fuses.

ok, im not going to give up just yet.  Thanks for all the help.  I got a little frustrated earlier when  I got no help from the manufacturer of all people.