It may not matter much for a small trailer. Find the gross weight limit for your trailer if you can. Then use a pickup that is rated to handle that gross.
It doesn't seem to much matter much whether you are towing withing the mfg limits. That is, until someone that you cause damage or injury to hires a lawyer that makes an issue of you towing beyond your limit. Then it really matters.
If the Gross Weight of the trailer (or the weight you normally run it at) is under 5000 pounds, and the 1/2 ton truck does not have a lot of stuff added to it or carried in it, you may be safe (you would need to look at the weight limits of the truck and trailer to be sure). If you have a diesel or huge (454/8L) gas engine, it may even be pleasant to tow.
Generally though, a 1/2 ton is not a good 'tow vehicle' except for pop-ups, small water craft and other ultra light trailers. For a 'small' (under 30') travel trailer, a 3/4 ton with a strong diesel (optionally a huge gas) engine is your best bet. Extended cab is real handy, and for a short travel trailer, the short bed should be as good as the long bed. 4x4 is personal preferance, and dual rear wheels should not be necessary for that small a trailer.