Umm, I built a 110-high acro tower with 10 landings, in my town, with a bed on top. I also bought Ghast Tears and made Potions of Regen (2:00). So along with normal health regen, the Potion and town regen stacked. I also had Feather Falling IV boots, and did /home bed when I reach the bottom, which gave me a quick way to level up Acro. In my experiments, I gained around 7,500 Acro XP per bottle of Regen.
Before I continue leveling up ...erm, profusely... I'd like to ask--- is this considered an exploit?