You need to take a hard look at your current trucks payload (yellow sticker inside the drivers door). With the limited tow rating you have I suspect that your payload is probably around 1200# {or less}, and when you add the proper tongue weight and the weight of the hitch which should be around 750#, you are probably already just about out of payload.
Going to anything larger just does not look promising and that 4.8 is already working pretty hard with the trailer you have. I too am no fan of slides as they are problematic at best and add a lot of extra weight. Look for a floorpan which works for you without a slide and your life will be much simpler.... not to mention lighter.
As always.... Opinions and YMMV.
:C