Hi,
I decided to go a different route for my extended CRT.5 and opted for the OFNA extended Chassis
http://www.amainhobbies.com/popup_im.../18750/image/2
The chassis is approx 15mm longer versus RCM's 40 - The chassis increases in weight from 142g to 204g and is also slightly wider and allows for a full size servo.
The kit was really well put togther and came with what looks like complete set of screws for the car (even though you use the old ones). The chassis is also slightly wider but not enought IMO for me to lay the battery pack flat.
The key benefit for me was the full size servo (645) and retain the ability to to use the stock bodies. All you have to do is flip the front mounts to the back of the upright and fits fine.
Also upped the pinion to a 16T/46 with a 3500 Feigao L on 3S 5000mah so it should fly...
I'll see how it runs in the AM if the snow holds off.
Cheers!