I have used the Vinyl Flat for several years. Initially I would borrow from a friend that has one about 10+ years old. I believe that pouch only had low and high. I would use the high, regardless, for about 3 hours and worked well. I eventually decided to get my own and the high setting for 3 hours melted the grooves. It was pretty wild and thankfully nothing special. I went to medium for about 2 hours and eventually found the sweet spot of medium for 3.5 hours.
My experience is that this works well for new vinyl. Any of my collection of older vinyl I have not had any success. I don't have as much of a problem with older vinyl so there's that.
Pressing plants basically suck for new vinyl as it can be so awful right out of the sleeve on new releases. I used to return them to amazon but got tired of the fight as the replacement was often the same. Now on new vinyl if it is warped at all, it goes right in the Vinyl Flat for the 3.5 hours and is all good.