In your single instance above it seems to of been bad luck/randoms, the instances I'm thinking of are when you slow to ~250 or less. You do seem to of been doing a low G high-alt turn though, just with minimal climb since you seem to be maintaining a consistent speed.
I've observed flak to be on average less-lethal at the speed and altitude you're maintaining, but working against your favor is the fact that bad strikes can still happen, and mossie bombers are delicate, especially with such a large open glass canopy.... still, maybe they're too soft or another issue with puffy damage, but that's a different issue.
Personally, when I fly fast or soft bombers like the mossie to the strats or over a CV, I fly straight through the puffy after my drop, to maintain the highest speed and try to just fly through the puffy until it stops or significantly lightens, then I do my 180 turn or skirt around my target avoiding the puffy as I RTB. I'll still take hits occasionally, but I would be curious if you could try it sometime and tell me if you think it makes any difference for you on a couple sorties.
Edit: Yeah... you might just have the worst luck Scherf