You are better off getting pretty heavy in the throttle to get your trailer up to speed. You are wasting fuel and heating the transmission up more than necessary by getting up to speed slowly. Also the chances for something slipping in the transmission are more with light throttle. My recommendations are for 300 HP and less BTW, more than that and all bets are off.
CJ, I would bet that you are getting an occaisional second gear start. If it is starting in first you should be able to take off with no problem once you get some boost on it, second gear will labor off the line. Call Bill, he will get you fixed up.