377PETE,
Awesome build! You're doing exactly what i want to do (convert a semi trailer to a durable, comfortable RV). I am considering using a moving trailer (i.e drop deck). The side and rear door openings can be easily closed in for windows/normal sized doors/slides. My biggest concern is trailer height. Every moving trailer I've seen is 13'6", preventing installation of anything on the roof (i.e vents, antennas, etc) without making recessed in the roof. This could be overcome by using flush mount side vents and other solutions, but 13'6" is still huge if trying to get into the average campground, park, etc.
What is the height of your trailer and how are you planning to route your utilities that are normally roof mounted? Also, what was the cost of your trailer (I'm trying to get some general costs to create a realistic budget for my build)?
I have also been considering the addition of slides. Looks like you have already found what you need but a couple of good sources for linear bearings and slides, gear racks, etc are industrial suppliers like
MSC Industrial Supply Co. and
www.McMasterCarr.com. If you have good design and fabrication skills you can build a bulletproof slide mechanism for a fraction of the cost of the lightweight units. Great project!