I'm in the process of designing some side mounted stowage, for my Blitz2, similar to yours, but the tops will be hinged on outside edge, so they can be opened whilst sat in buggy, and the lids will be slightly angled downwards/outwards to discourage rainwater flowing into seats on corners!..... also I'm gonna fit an elbow pad, on the rearmost end of the lid, to protect my funnybone, when driving off-road......