downtube boss for Giant TCR?

[Gsk]

I am wondering if anyone makes a clamp-on downtube boss that would fit a TCR downtube. The reason
for this is to be able to use a Profile STI adapter to allow shifting on the rear derailler from
both the STI and at the end of an aerobar. The Profile adapter is a cable splitter that allows
shifting from both. However, it needs to be mounted on a downtube boss. The bike is being set up for
triathlons. Has anybody tried the Profile STI adapter for this purpose? Here is the product:
http://www.profile-design.com/products_brakes&shifters_stiadapter.html