If you think your boom can take the drilling I would definitely go for your preferred idea of down the sides without a doubt, this is how my last boat was.
I would have much preferred to have used P strip down either side of the boom this time but my thoughts were that the boom was most probably too fragile to stand all the drilling for the fixings.
For the closing flaps on the bag I have used Velcro in one run all the way down. I did this because the last boat had it and this seemed to be all but watertight especially if the boom had a fall aft. Plus I find it's so much easier for opening and closing than a zip.
I would have much preferred to have used P strip down either side of the boom this time but my thoughts were that the boom was most probably too fragile to stand all the drilling for the fixings.
For the closing flaps on the bag I have used Velcro in one run all the way down. I did this because the last boat had it and this seemed to be all but watertight especially if the boom had a fall aft. Plus I find it's so much easier for opening and closing than a zip.
