Italian Stallion,
I built a HF trailer as well and made my tounge nice and lont (space for cooler rack later!). Longer is ok... Just dont get too short. mine is a littel more than 2x the axle, and worked great, has about 1000 mi. on it now!
The longer the tounge, the less tounge weight you have (important if you put a 35 qt. cooler full of ice on it!), you just have to make sure that the tounge doestn't get too light, It will track funny!