well we've had our first serious rain since i replaced the felt, and it doesnt seem to leak. phew also the 'waves' didnt seem as bad when i re-inspected it, and the thicker bitumen where the waves are is solid, so no point trying to clamp down or alter it in any way.
ive ordered a couple of 3x3 fence posts for a tenner which ill 'jam' under a couple of joists in the middle area of the roof between the joist and decking just over winter when we're not using it. that should give it enough strength to withstand snow. when the winters done ill just remove them until the next year. seems a cheap enough compromise for a belt and braces approach. the roof may be strong enough anyway, but no harm in being extra sure
thanks for all your help chaps.
EDIT: apologies for large pics, couldnt make them smaller.....
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