Imo I think round tubes are the easier rails to slide, if it's a thin circle rail it's easier to hit those if they are down rails I feel, if they are set as flat rails the balance is a bit harder but not by much. For fat tubes gripping them for spins and swaps is great and they are my favorite type of rail to hit. If you are doing a straight slide there is not really any gripping that happens, the faster you Come into it the less balance is required. Hop on keep ur head up looking at the end of the rail and keep your shoulders square