Hi: If you are going to cut accross the grain, as in doing door rails you will need something to guide the wood. I would suggest that you look into a sled that allows the work to be clamped down for feeding through the bit. Some of the sleds use a miter slot as the guide, and some others use tyour fence itself to guide the work.
Rockler, Infinity, and others sell these sleds. The one from Infinitytools, has a base plate made from 3/8ths thick aluminum, which should be about as rigid as you would reequire. Hope this helps. Woodnut65