Did a quick test. With 402 PIE, you can get off a B3 with 4MP left using (Sharp) F1 > (Eno) F3 > F4x2 > F1 > F4x3 > B3. Then you wait for the tick, T1 and continue along your merry way. If you never ever plan to use that setup, you save 618 MP by doing B3 (tick) > F3, which is ~91 PIE. I believe I'd calculated the exact amount of PIE needed pre-3.2 but used 6.75 MP/PIE instead of 6.8 so I was a few points off.
