Actually a small manufacturer rather than a custom builder, so there isn't full flexibility. I have expressed the concern, yes. I'm expecting a response next week.
I use a car-trunk rack to transport bikes when I'm taking more than two. Since it clamps on the TT of the bike, I think I should get a stronger steel if I can. I haven't signed up for this bike yet, but it is a good geo, and I like the standard diameters.