New 'Vinyl Flat' flattener?

I tried mine out today with the pouch. 5 hours heating time and a couple of cooling hours. Pretty severe edge warp gone in a new pressing of Lucinda Williams "West" which all four copies I tried were next to unplayable. So far, so good.

After flattening, is there any negative effect on the sonics of the album? In other words, is there detectable groove damage?

My first attempt at 5 hours on a severely warped (it was unplayable)new 180 gram LP did not work. It appeared it may have improved somewhat but still pretty warped. So now it's in for a second run....

Based on my understanding from conversation with Vinyl Flat, multiple rounds may be required for more warped records. Especially 180g I would expect.