It's good to know, bdodds. Thanks... It happened I found last weekend this used Studiologic SL-880 for a very reasonable price, and having this Fatar keybed, I thought it could be a good idea to try it out.
By the way, yesterday I got working the rig, with Piano on 1&2 and Organ thru 3 (mono). It's absolutely easy to play with/without external 88 keybed, you just only need turning on/off the Dual Keyboard function.