Lou,
There are a couple of things that you should keep in mind about what coax you use. Unless for some specific reason, the characteristic impedance ought to be the same as the 'rest' of the antenna system, typically 50 ohms. It ought to be able to handle the power being used. At 250-300 watts, that's almost anything larger than about 3/16 inch in diameter (not the best way of gauging it, but close enough). And it ought to physically 'fit' in the space available. If it'll do all that, it'll be just fine. If it won't do all that, it's time to rethink how and/or where you're going to put that antenna.
From what you describe, the thing to work 'around' is making sharp bends in the coax, just not a good idea with any coax. It also sounds like drilling visible holes isn't an option, so how about 'hiding' one'a them holes for the coax to go through? Probably a viable solution if enough imagination is applied to it, sort of.
Good luck with it!
- 'Doc
