The transfer tubes in TCs are held with snuggly with grommets. There are no attachments to the frame.
Turbo, I think you should use the grommets that are a snug fit in the frame and where the tubes are a snug fit. In other words, I would use the approved grommets from one of the usual suspects (DBE, rd, Lotus Supplies, etc.) and get alloy tubes with the same OD as the stock tubes.