Rails not needed. I would do a 1.5XTR in 10cm rather than the 440XT, but please note, I and many others have had awful experiences with Blouch when it came to service. I could not even get them to reply to email about parts or cores when I offered to pay for everything, so you can imagine how warranty inquiries are handled. If you don't live close to him, I would choose something else. But, I hear you say, the 440XT is needed to fit the stock intercooler the AVO replicates! And I will tell you, nothing in the stock TMIC footprint will properly cool anything in that power range! You are trying to put 10lb of shit (hot air) in a 2lb bag (intercooler). You need to be thinking minimum GRB TMIC with suitable splitter or better, a FMIC at this point. And please, ditch the UELH. That robs you of so much power and efficiency. ELH or go home.
Glad to see this thread is still alive and kicking after all this time!