Mace, I found my Ziroli F-4 plans. I did write down notes on it too, believe it or not, regarding CG. Actually, I'm not surprised, since I was surprised how off it was for me... You may want to compare this with your plans, because it is possible the CG location was adjusted before it got to Larry. I'm guessing here. And if Larry chimes in, I'd take his word first. But this is what I noted regarding CG location. As you can see per my sketch, I moved it about 1" fwd of the spot called out on the original plans, after numerous takeoffs, rotates to about 45 degrees, then the airplane "hang", where the tail is totally blanked from flow, and very little fwd velocity.

My model was just a tad over 4.5 lbs - it was quite lightweight - Dave Brown lite wheels, no rudder, etc... When I switched to the OS 46 / KressFan, I'm sure it picked up another 5 oz (pure guess). This was like 1989-1990 for me. I've considered building another, possibly for electric if I could get a canopy. Lightweight retracts would also make it fun. I also found my single, lone photo of the model - I'll see if I can scan it tomorrow and add it here for fun. [8D]