G'day orangeandgreen. Yes and no... firstly, I did this on the recommendation of the bloke who sold it to me (or re-sold it, as it came from China). He'd had a number of previous sales break due to the original configuration and this suggestion was the work-around. Secondly, due to the weight of the loaded (water with a wee bit of anti-freeze) drum on the four bearing mounting bolts in the suspended (underneath) configuration, it would quickly (time wise) shear the bolts with the constant up/down & tractor manoeuvring wobbles/vibrations when setting up for the next pass.
Supporting the bearings on top of the frame reduces those stresses. The aerating spikes are bolted on as a 'strap' and can be removed if I simply want to roll. The other option would have been to purchase a towed roller, but I have small horse paddocks with limited manoeuvring space to utilise that type.