Thanks for the input. The high aspect ratio would be a help, but one of the pre-requisites for any twin I build is that it use the two nice 25FPs I have already. My biggest problem is that I have too many "mind" projects as you put it... especially for classic stunt. Matching engines/plans/classes is a nightmare when there is only room to build one at a time!!
I'll definetly build an He 219 for the two 25s one day, but the question will be whether to build it pretty for F4B or profile scale or build it super light for classic stunt. Leading odds are with the original plan of doing a profile scale He219 and going with the little Hooptee for classic. There's a Rabe Bearcat plan yanking at my chain for classic though... If I had a spare ST46/60 lying around it would be a done deal
Let me offer a couple of ideas.
1. If you are only interested in profile scale but with limited maneuverability, you might want to look at the article on the He 219 by Joe DeMarco in the May 74 issue of Flying Models. This is a profile for two .15 engines. 38.5 inch span. and measures just less than 200 sq in. Thin airfoil, no flaps. It captures the look of the He 219, but the wing planform is "simplified" somewhat and does not have the taper ratio of the outboard panels. This model appears to be more for "sport flying" than a serious profile scale entry. It might be capable of some basic maneuvers, but would not be any serious airplane for doing the full pattern.
If you want a semi-scale profile He 219 for competition stunt, it would make more sense to draw up your own and make the trade-offs you are comfortable with on how much scale you want it to be. If you are using two .25 engines, a comfortagle wing area would be somewhere with something less than 600 and 650 sq in. You could go bigger, but to no real advantage. In fact, with the .25's, 575 to 600 with a decent weight (less than 55 oz) would probably work surprisingly well. (As Ted Fancher suggested, the extra propeller contributes significantly to the performance of a stunt ship.) If you do your own, you might want to look very closely at the work that Al Rabe does with his semi scale designs.
2. Regarding your comment about the Al Rabe Bearcat. Al's design from March 1970 American Aircraft Modeler is Classic legal. He flew this airplane to a 2nd placeat the 69 Nats and another 2nd at the 70 Nats. With the right power plant, this is one of the better flying classic ships you can find . And Al could probably help you with an improved version of his Bearcat that is still classic legal with a slightly different airfoil and lighter construction. Keep the weight within reason. (60 oz would be at the upper end.) The ST .46 is a good engine and has been used successfully in this airplane. However, there are now better choices. A PA 51, or a Jett 50 or a ROJett 50 would give this design the extra boost that it needs. A .60 also works. I have successfully campaigned my Gulfhawk Bearcat with a Jett 50 for 5 years in classic. (VSC 1st and Nats 2nd in 2005 classic events.) I use it for the Open events as well and it has performed well even against the "modern" designs and the tuned pipes. (Finished 20th in Open stunt at the 2004 Nats.)