The side thrust is probably to counteract torque at high throttle settings.

I'm not a fan of any down thrust on any model. The problem with trainers is all of that extra angle of incidence put in when the leading edge is set higher than the trailing edge. Also, the flat bottom airfoil is at work too. So, downthrust is there to provide some sort of fix to keep the trainer somewhat level throughout the throttle range where it won't balloon up on you.

I've not owned a bipe from the era of your model, but I've seen enough flying to see that they have a lot of slow speed lift. Drag is probably very high. You can always use shims if the angle is too much.