I'm fairly new to the Jeep world, (95 with 2.5 ltr), and I am in the same situation that you're in. I chose the RC because of cost, and the install seemed to go fine until I drove it. Vibes were very bad and RC customer service told me the same thing, that it didn't need any sort of TC drop. I ended up spacing the TC 1 1/4 inches, but it looks terrible and there is still a bit of vibration from 25 to 35 and a slight bit going through 45 mph, but it is driveable.
RC has been very consistent telling me that the 2.5 inch lift on the YJ requires nothing in the way of modifications and that I should not have any vibes.
I've decided not to compromise and am in the process of installing a JB SYE and will be ordering a new driveshaft this week. FWIW, JB was not surprised that I was experiencing vibes at just 2.5 inches.
Personally, I think any sort of lift project should be looked at with an SYE in mind. It just makes little sense to raise a Jeep only to lower portions of it to make it driveable.