i had A5, did quite a bit of testing and found no noticeable difference so always used it during racing. the advantage was looked good. saved taking on so much water during a stuff. disadvantages are something else to break or fall off and pain when you need quick access to the rear.
I can build them if anybody needs one.
he's not he has gone into making rings we also had a infill on are argo 19 we found in the flat it caused down presure but in the rough it worked to are favor because it kept the boat down more any way i might be wrong thats just wat we found but they do make the boat look better.