mmitch,
As many as 50% failures on a BFTS Course ? That really surprises me, but I wouldn't question an authority such as Brian Trubshaw. Even so, to expect solo on a PT-17 after only 5 hours ab initio would be ridiculous. Perhaps the UK Grading Schools were up and running when he finished ITW, and his Class had already had 5-10 hours on Tigers before they went out. My memory of the PT-17 is that, as heavier and more powerful than the TM, it flew much the same but without the "float" on landing.
The BFTS two-stage syllabus points up what I've written long ago: that the third USAAC "Basic" stage of training was superfluous, although all flying experience is valuable and we had an extra 70 hours. But no noticable improvement in the end product was ever claimed or observed.
Danny.