thanks mate, I ended up getting a very good ST3000 and put the gas conversion gear on it, timed it up and it is performing very well. 18x10 bolly at about 7200 RPM, it is ripping the P51 off the ground with great authority, fast in the air and excellent vertical. Very happy with the combo.
It was only slightly longer than the 2500 and a bit heavier. Removed spacers and moved battery packs rearward.