use tape to mask off the lines then get a cutoff wheel and u can get a perfect straight line easier. jigsaw is second best. but cant really get in tight if u need to.
on the "v" top tube swingarms. how does the carrier tube hold up from twisting with the top tubes center fitted? with no top support for the carrier. just curious?
i dont doubt u windy. ive just never seen that happen with steel arms. u say it like anything built with mild steel is junk. which is so false. chromoly has its own problems as well.
ive never had a problem with mild steel. i highly doubt thats the problem. what size wall are these ebay arms? the reason u need gussets and straight through shock mounts is because its so thin. simple as that.