If I'm not mistaken, Faris used the ventus bar in Kona. At the Cannondale tent in the expo, his mechanic was working on how to mount the power control. He was trying all types of stuff and this was two days before the race. He said that 2 years ago, they ended up duct taping it to the bars. Anyhow, my point is to try to look at photos of Faris' bike and bars and maybe you'll get an idea.

Velcro if the extensions are close enough to simply mount the PCx on top. I've used that setup all year w/o any issues.

Faris used the Xentis bar - not the 3T Ventus - at Hawaii. Either way, velcrox may be the best option or mount on the extensions using a Profile (or similar) bike computer mount kit.

problem is that the extensions are spaced to narrow and you cannot really use regular mounts.

I used a hotel key card as a platform, two zip ties to tie it down, some velcro to hold it, and a drill.

I saw a number of athletes (Craig Alexander included) were using SRMs plus a Profile Aero Bottle.
Anyone see any pics or know how the powercontrol units were mounted?