Hi Gordon,
I would suggest looking at the SRAM DualDrive option instead of changing the
boom. The DualDrive offers a 3-speed internal gearing with a ratio of 73%, 100%,
and 136% of original gearing. This would match a triple chainring and still have
your external gearing also. All shifting would be at the rear wheel for more
efficiency. It works really smooth and I had installed one on a '03 Catrike
Road. I was able to pull a 70# load behind without any trouble. The only time I
could sense the load was on downhills when it pushed me along. It would involve
having a wheel built with the new hub but it eliminates the hassles of front
deraillieurs. The system shifts smoothly under load or at a stop. It uses the
same idea as the Sturmey Archer internal 3-speed. Can be shifted while stopped
for a smooth start even from an incline. They offer a single control to operate
both the 3-speed internal and the 8-9 speed external gearing cluster. You can
see my trike at www.webshots.com. Under advanced search enter beagle77 for
member search and look in the Dale's Bike Shop folder. The first recumbent is
also mine and I tried the DualDrive system on it first. It worked fantastic too
bad Trek only produced this bike for 2 years. It is harder to start on an
incline which is why the DualDrive was a nice option for it. I didn't take any
close-ups of the install on the Catrike but at the end of this folder are pics
of a Trek SOHO that I have the drive on. This particular bike id not have front
shifting and I opted for this set-up as I have never been impressed with front
deraillieurs myself. I was working at Dale's when I decided to experiment with
SRAM's system. I was not disappointed with any bike I tried it on. Hope this
info helps give you some ideas. I guarantee you would not be disappointed either
with this option. Take care and good biking. Brian Eagleson.