Furutech / Air Tight LP Flattener - do they work?


I am wondering if anmyone has actually bought used either of these LP flatteners and how well they work??

I find a lot of general new releases are dished, so record clamp works great on one side, but not on the other due to the dishing?.
Do they flatten dished or bowed LP's.

cheers
downunder
Forgot to mention,one other friend has the Air Tight unit.He claims it works great.....Yet,for thirteen bucks I made a superb(looks great too)DIY flattener,that seems to be quite effective.

I took two nice pieces of marble/sandstone slabs(12x12 inch),which can color match to almost any room decor.Found at any good Home Depot type outlet.

I then attached a sheet of self adhesive cork liner to one side of each.This gives a slightly pliant aspect to the two pieces and when put together will not hurt grooves.

Just use gravity,and maybe a nice warm windowsill for a few days(not alot of heat,which scares me)and my three LP tries have been quite effective.Mostly on dished LP's so far.

I am sure the expensive Furutech and Air Tight units are better,but my DIY'er looks really cool,takes little space and is effective.

Best
It is puzzling at times to buy a $2k disc flattener and you are flattening 99cent LPs or even $30 new releases LPs. Question is how often will one use the flattener? My take is I'd look for another 99cent LP and I'd return the new $30 LPs and ask for a replacement (I assume you are buying them new from reputable vinyl sources such as elusive disc, music direct etc). Sir Speedy's method is as effective I am sure. Just my thought!