The thing about the Rangemaster is that it has some kind of RS485 data link to keep the transmitters in sync. I'm not really sure how (or if) it works, but that would be very helpful if it did work. It is also FCC approved and only comes prebuilt. There are limits on the number of homebuilt transmitters (5?) that you can run, so you could run out of "legal" transmitters before you reach the end of the project.
I'm just starting down this road too, so I can't offer much more help than I've already done. I can tell you what my plan is:
Start with an SStran transmitter kit and build the antenna that he outlines on his site. Put it up and see how far it will go. Thankfully all this is easy for me since I've worked as on engineer in the TV industry for the past 16 years. Now I'm working at a local college doing most of the same things, and a bunch of new stuff. Hoping to get materials ordered in the next couple of weeks, and get it built, tested, and ready to mount by the time the weather gets warmer in the spring.
I'd offer to help build stuff for you, but I'm pretty swamped with things at work and at home right now.