trikes come with 30 70 gearing - its pretty easy to go 30 - 68 on a 07 bike and use a stock belt but its a pile of work to do plus its not exactly free.
Timo,
What is the gearing on your '07? 30/66, or what? I have the DD7, which I've used in a SEUC3 and an FLTRUSE, and have towed a Bushtec Turbo +2 (fairly large, heavy trailer at max load) with and without the gear change and the tranny change.
Before I put the dd7 in the SEUC, I replaced the front 32T pulley with a Tri-Glide 30T, which changed the ratio from (66/32 =) 2.0625 to (66/30 =) 2.2. That made 1st gear (and the 5 others) 6.7% lower [(2.2 - 2.0625)/2.0625 = .0666 = 6.666% = 6.7% rounded off]. That helped markedly, but...
In comparison, the dd7 1st gear is 12% lower than our stock 1st gear, nearly twice the change of 32-66 to 30-66. But wait! There are more benefits than that, since its top gear is still 1:1 like the Cruise-Drive. With the "tooth loss," that meant more RPM in any gear, at any speed, than stock--enough to be noticeable when running 70 to 80 mph. Also, since the dd7 is closer ratio between gears, there isn't as much RPM change when shifting. I really like the effect it has on the bike; makes it much easier to get off the line, much better for slow maneuvering, and you don't get caught in the middle as much, where one gear is too low but the next one is too high.
The only dd7 drawback so far is that cruise control works only in 7th. Apparently there is a fix for this with TTS (which I have) and Daytona tuners, but we haven't zeroed in on exactly how to do it.
Hope this helps. Sorry for the
Bryce