While is it nice to get the soil perfectly smooth...you will be digging trenches for the straps in a buttress free system and adding breeze and at least 2" of sand on top of that that needs to be smooth. Ours isn't smooth at all and while I don't think it hurts anything other than the effectiveness of the auto cleaner, it's just an asthetic thing. When we replace the liner in 15 years, I'll probably either smooth it much much better or put down a bottom liner.