I just realized that the axle mounts that I welded on are not right for the axle that I have, widthwise. Made some assumptions that did not turn out to be right, unfortunately.
Since I need to put the mounts in new locations, I think it would make sense to go with new springs instead of the ones that just happened to be on the frame that I acquired since they are designed for a trailer much larger than mine will be.
Anyway, to my point: I can put the mounts wherever I want now, so I can get any length spring, I suppose. After reading http://tnttt.com/viewtopic.php?t=31865, it seems that I should be shooting for around 700 lbs for each spring ( my trailer wouldnt be much more than 1000 lbs).
But what about length? There is a wide range of spring lengths. What are the advantages and disadvantages of shorter and longer springs?