Hi,
be carefull, ANY discontinuity you might create with that line, intentionally or unintentionally can cause brake down (steps, bends, Tees etc.), calculations for power handling are valid for uniform lines only, standing waves have minima and maxima that can be critical. I used to work with that range of power (but larger than your case, 100W) and have regulary a fire to put down because the N connector to microstrip transition was hard to match perfectly. The problem was solved with replacing microstrip with stripline. Just to let you know, my microstrip was 50 Ohm so the problem was much easier to solve. Furthermore, microstrip of such high Zo is not recommanded due to high conductor loss, so even the power discipation on uniform line can be a problem)
Hope this helps, didn't mean to frighten you.
flyhigh