Good afternoon gents, I'm planning a mixte build for my wife and wanted to make sure I was on the right track regarding the twin top tubes. I have 1/2" .035 but it feels pretty flexy. Is that sufficient for this type of build? Cassave used it on his build (sticky thread at the top) but I just want to make sure it's strong enough. She weighs around 115 and will likely have our son up front in the kiddy seat.

OP; Put in a couple of braces or bridges to add some muscle to it. 1/2" 0.035 would be ok for a small frame. If the frame is in the middle to taller sizes, I would use 5/8" and .049 or something like that.

Great, thanks ksisler. I'd rather move up the diameter a bit to stay on the safe side.

My thought about step through frames is that putting a large tube in as a top tube and then having an extra set of stays is the best way to go. The double top tube design is not that great