Congrats on your "gifted" Cardinal. Is this the ARF?
I'd check the wing centerline join to make sure it is adequate. The one I rescued popped apart there. Of course, it had hit the ground before it went into the garbage can. And I'd check the incidence alignment real careful before you start covering and painting. along the same thinking, I'd pull test it first thing--especially if the controls are all covered up already. Or cut a clean hole and take a peek inside. In the last year I have worked on a number of OPPs and 3 of them had some major issues with the bellcrank. Either it was not bolted in properly, or the pushrods were not really formed well and caused control slop, or..... Check it before you spend time finishing! And if the pushrod is not a one-piece music wire job, I'd check that really close, too. I have the salvaged controls out of another garbage can plane where the soldered coupler let go on a brand new airplane. Hate to see so much good work go to waste because of a control failure.
On my "garbage can Cardinal," I had to make new flaps, so I made them a bit narrower, as recommended by the West Coast Contingent. I had to build a whole front end from scratch, and followed the kit plans. It was unhappy with a OS 46LA due to resonance. I fiddled with the nose by making it even stiffer, but I should have gone the other way. It actually was happier with the OS 40LA with much more consistent runs.
As far as flying, when it was running smoothly, it flew great. You should have good luck with yours.
Divot