Hello mmathias3,
As some others have pointed out, the short bed on the MegaCab is the same length as the other short bed options on Dodge Trucks. I tow my Heartland Landmark with a short bed quad cab. I have a normal 18k signature series hitch in my truck, no slide and have never had a problem. There may be situations where I might have gotten backed in with fewer pull-up/back-up iterations if I'd had a slide-hitch, but I assure you it is simply not required.
Back before I purchased this setup, I ran a poll on the forum. You can see the results at this link, but it basically came down to 84% of the respondents not having ever used their manual slide hitches. ( The full thread is available at this link.)
Enjoy your new coach, and your Mega Cab! ( I really really want the new 2010 Dodge Crew Cab!! But, alas.. my '07 QC will last many more miles.. )
Thanks,
LK