All aeroplanes twist and groan as you load them up. The lovely little machine I learnt on years ago (Millicer's Victa Airtourer) had the tailend tin gauge increased to ease marketing concerns about the extent of oil canning - so long as the relevant maintenance and inspections are done on the Tomahawk and the pilots operate within the anticipated design envelope, then it shouldn't be a concern if the tail deflects during a spin.
More importantly, to learn on a comparatively demanding aircraft makes a great deal of sense. In my insular view of the world, I think we all should still look at spins and basic aeros - even if just for the confidence building value .....