Burley Recumbent with GEBE
Sorry I did not respond sooner, but did not receive notice of activity or missed them???
Question responses: By "seat stays" I believe you are referring to "speed struts." No moving was required and engine sat nearly vertical or slightly forward, which is (my) preferred position - looks better, may be more efficient and weight near rider reduces wobble factor.
Frankly, I added struts later and no problems were encountered with motor, though I did have to fab two mounts where stays meet seat at top seat bar, which is shown on above links I believe.
Regarding the long ride. The bent is comfy save the feet being up and hills, and the CF is almost as cushy for rear-end. You can add a shock absorbing post to Gruv, which you cannot do on Rans CF or bent, if frame not flexible enough to absorb shocks.
The CF configuration reduces or eliminates the wrist-hand-arm tension of a conventional DF frame and makes longer rides easier. It is more of a balance between leaning forward and leaning back with pull on bars, as when climbing hills.
Anyway, install was simple. Required obtaining 36-spoke rear rim and longer throttle cable. As the pics note, I used a fabricated engine mount bar and a side bar to hold bag, and, as a side benefit it also serves to stabilize the entire rack system when attached to frame - a pair would eliminate the center engine mount bar.
The frame etc was completely compatible, but that may not be case with other makes.
I might add, a season later, I am glad I now ride the Gruv 2 Raleigh CF bike rather than the Bent, supremely easier starts and hill climbs, which I never could do and starting on hill was impossible, and much, much safer in traffic.
I was going to install on Rans CF, until I read DougC's comments on his install of GEBE kit on Fusion. A bit of research and luck landed the Gruv 2. Would not go any other route now.