Actually, the shortbed on the Mega Cab is identical to the quadcab shortbox, at least on 2007 models.. I measured and checked the mfr's figures before we purchased the 2007 megacab. Maybe it's different in 2006? The Dodge shortbed is 2 inches shorter than GM's and 5 inches shorter than Ford's. However, the length difference is behind the axle. Cab to axle center, where the pin goes, is within a fraction of an inch the same in all of the shortbeds. So proximity to the cab in a turn is nearly identical on the mega cab and the quadcab shortbed.
I've been using shortbed trucks with a slider since 1995 and never had this problem. But, then, I am constantly aware, when turning, that the possibility of collision exists. I'm paranoid about it enough to never forget. If I think I'll be close, I have Vicki watch the cab/FW clearance and sometimes I'll get out and check it myself.
With the new Montana nose, turn radius is so good with a shortbed I doubt I'll ever need to use the slider again.
this is without using the slider