TT Trainer is a flat bottomed wing like RCM trainer if I'm not mistaken. Efficiency of these aerofoils mean that small increases in either airspeed, thrust and angle of attack will effect large changes in rates of ascent causing the 'balllooning' you describe. If the incidence angle of the wing is mistakenly cut into the wing saddle at the 'factory' marginally higher than it should be as it commonly is on ARFs, the problem is exacerbated.

Secondly, overpowering the models (excess thrust) doesn't help either, but that's beyond the 'ken of the aerodynamically and instructionally illiterate who sell you the stuff, and many albeit good intentioned who would 'advise' or 'instruct' in good faith. A case fof the blind leading the blind, except the one doing the leading often isn't aware he is.

Make sure you've got the recommended downthrust angle factored in, though it shuold have been factored into the firewall with the TT ARF. However bear in imnd that downthrust is a poor aeromodelling kludge which will only work at one particular power setting and flight attitude, and for any particular model is set at an angle intended for the intended engine to be used in that model at a single power setting usually determined to be full power in straight and level flight. So if you are using an engine developing greater thrust and pulling the aircraft faster at full power than that down thrust angle was calculated for, eg:TT FS-54, you will need If you will need to increase it, which will of course exacerbate the differential when you aren't at full power. In either case, you will have to trim out the changes in power and speed with greater trim changed required more often with increased downthrust angles and more powerful powerplants in a model with a wing like this really intended for moderate plain bearing powerplants like an O.S. 40LA, TTGP42 or Enya SS40.

Nose weight won't assist your 'ballooning' situ at all. Adding nose weight alters the CofG forward, which willl make the model more pitch stable and less responsive to elevator effectively increasing the degree of trim or elevator input you will need to make. This is immaterial because it's not pitch instability which is the root cause of your apparent balloning problem.

On very gusty and windy days two factors will affect and exacerbate the sensation of ballooning. One is real and the other illusionary. On gusty days when poiinted into wind, the RAF or relative air flow often actually strikes the wing at a slightly increased angle of attack due to orographic effect which we can't escape given our proximity to mother earth and the friction layer in the nature of our ordinary operation. This creates additional lift (increased ROC or rate of climb) and the aircraft climbs unless we reduce power and counter it with a little down elevator and trim it out. Again the efficiency of the aerofoil on the TT trainer accenuates this climb even with a small AoA increase. The second is due to increased climb gradient or angle of climb as your model tracks over the ground. The groundspeed is severely reduced up wind compared to downwind and is visually noticable from your perspectvie though the actual airspeed remains effectively constant. Thus you see the aircraft appear to balloon or gain a lot of height in comparison with distance travelled over the ground when flying upwind. The apparent 'ballooning' is an illusion due to model gaining greater height in the same time but over a shorter distance increasng the climb gradient and steepening the climb angle due to that differing groundspeed upwind caused when flying into a moving air mass (wind) heading in the opposite direction over terra firma. THis of course provides the illusion that the model is climbing faster when it really isn't, well, not caused by that anyway, but by the changed trust-line and increaased effective AoA. All conribute to making the model appear to balloon and climb like a rocket. Even properly set up flat bottom winged models in such conditions are annoying to the veteran flyer, and posiitivily disconcerting to the confused and struggling beginner.

All you can do with your current setup is try and understand what is happening so you can counter the effects as necessary by inputting the correct corrective inputs in to counter the effects described. Those physical realities described are always present, but are markedly reduced with a symetrical aerofoil and higher wing loading type. The problem is exacerbated by overpowering the model usually attributable to a beginner receiving poor purchase advice and not infrequently, poor instruction both unfortunately all too prevalent in the hobby.