Welcome to the Family. Let us know if you have any questions. Hunter has about 9 gallons through his. I have about 2 gallons through mine. I am very happy with it, and will gladly help make your Fantom experience an awesome one.
The XTM .18 has gotten some good reviews from the one or two people I know that have it, and yes it drops in where the .15/.12 would on the T-maxx with minor to no adjustments above and beyond what you would do for any new engine.
As for the who I know that have it...a couple of dudes at my LHS.