RE: World models 80 inch p51 engine advice
I will add to my message above that even with the 3/8 inch rearward cg the ONLY issue I had with its flight performance was when it snapped out at the top of a loop. It did not snap when landing with this rearward cg with a "normal" landing speed. I didn't fly it again until I fixed the cg - I knew i had messed up the cg because I had previously flown this plane with ther spcified cg and it had never snapped like that, even when it had too little airspeed to complete a loop- it just dropped out of the loop and immediately was flying again after it gained a little airspeed. Also even after it snapped I had full flight control right after the snap.
I have found that this plane will slow down to a VERY slow airspeed when landing without dropping a wing, and it lands VERY easily/slowly even without flaps. This did not change when I had the cg 3/8 inch rearward. So I consider this to be a very good flying plane, on a par with any warbird out there, and as good as most sport planes and aerobats. To me it flies as easily as the 60 size mustangs I have flown - but it does require more room when flying and because it is heavier you need to paln ahead a little more - don't let the plane fly you- you fly the plane eh?
On the other hand I don't deliberately slow it to a crawl when landing as a standard practice. Sudden wind gusts etc could blow it over, etc. In crosswinds I always land faster.
Ed