The first two LT-40's in our club were flown witrh OS 46s and woukd just barely fly. Every other one built-ARF's or kits- were powered with OS 46 FX or AX. All flew like new planes. I flew mine on floats as well, and it weighed 7 and a half pounds with the floats on.
The LA is just not powerful enough nor weighs enough for this plane.