FYI, I found the rear triangle flex with the CS-036 problematic at a riding weight of around 180. Any significant pedal torque would twist the linkage and cause the top of the rear wheel to offset a half-inch or more to the right. Chain rub was constant as a result. (I'm certain this is intrinsic to the model. I replaced and retorqued the chainstay, upper and lower bearings, and spacers, to no improvement.) Note also that the CS-036 and Workswell 108 are single-pivot designs, so they're best paired with a suspension lockout system if you intend to ride out of the saddle.

I would suggest buying a used Felt. You can find carbon versions, fully built with decent kit, for under 2K. You'll be out around $800 for a CS-036 frame, plus another $200 or $300 for a decent shock. The savings over a used rig are marginal and you won't get much warranty support from the Chinese vendors anyway. If you're really XC-oriented, I think Chinese hardtail frames are a considerably better value.

I saw issues with flex and another user posted about sex bolt issues so i guess I will look into that. I have a hardtail Felt Nine 1 right now and while it is an amazing bike the riding in Arizona and Xterra is much more full suspension oriented. While I agree that overall I may be faster on a hardtail, if my legs are totally shelled at the end then the run is gonna be a rough one.

Is it a common issue for the frames to be very flexy?

Good call. By "aggressive" I mean geometry wise, steep head angle and made to go fast in more flat terrain. Im not really doing too much technical downhill riding. This is mostly so I can save leg energy for the run portion of offroad triathlon.

Carbon_Dude. You seem pretty up on these dso if you say the 036 is a good choice for XC stuff then i definitely believe you. Im not too worried about flex as I'm a lighter rider. What would your recommended company be to order from?