What trailer wt could I tow safely?

I have a 2006 Toyota Tacoma 4wd with the 4 cyl engine. I understand the weight rating issues (full timed for several years with a triple a letter fifth wheel and FL 60 Freightliner) Am looking at one of the small trailers like a TAB. Will meet all weight issues but what should I expect in terms of speed on hills? I don't have any need to be fast but don't want to be a hazard.