Yes, I collect the the water in the curved gutters too & give it back to the raised beds, when I want too!
Yes I curved it, yes completely mad I know, but a lot of fun too, the cover was easy, esp when only tension it on a very hot day(definitely don’t try on a cold or cool day). There are so many manufacturers out there, some are helpfull some are rude. I chose http://www.robinsonpolytunnels.co.uk/ & delt with Mr Robinson the whole time. I found he helped me every step of the way.
One clever thing I did by mistake was to buy one of his min-polytunel 8’x4′ which I can move around my raised beds, it teaches you so much about putting the big one up.
One bit of advice I read was to put up the biggest poly tunnel you can ‘manage’ & the next bit I would give is prepare for some ‘HOT BEDS’ too.
Seeing Charles’s Hot Bed in his greenhouse is just amazing, the freeheat proporgating & you get some compost 2 years down the road too.
Yes it’s worth-it & can be beautiful too!
a donf’ go for it