5th wheel slider length?

I'm specing my first truck and I'm wondering what slider length to go with. The company truck I've been driving for the last few years has a fixed 5th wheel and it works fine for the job I do now. I'm pulling tridem mechanical rgn and I'm quite used to loading it right weight wise, but I want to spec a truck that would have the capacity to pull a single jeep too. How much would I need to slide the 5th wheel forward (from center of the drive axles) in order to lift the jeep off the ground and onto the frame for when it's not needed? How much would I need to slide it back (from the center of the deives) to NOT take the mud flaps off turning with a jeep on the ground?

 

I'm going with a 14.6 steer axle on a 244 wheelbase. 18-20k steer or a pusher is out of the picture entirely and I'm not generally specing the truck to handle more than 135k gross. I figured 36" slider starting 8" behind center should do, but I'm not quite sure whether that would allow me to slide a jeep on top of the ramp when I don't need it and for maneuvering?

As far as the mud flaps goes I might cover both axles with single poly fenders and bold them right to the rear drive axle fender. Then it would require a specific frame ramps that would raise the neck right from the start of the climb, but I have something in mind already.