FACT - single sided elasticated girths cause the saddle to move/tip away from elastic insert. This movement is only small but it does over time cause soreness and muscle wastage.
I had hundreds of templates of horses backs and they all displayed the same characteristic hook shape dependant on which side the elastic was used. Of course, I used to meet the occassional person who would actually swap the side of the elastic every ride but this was very rare.... in fact possibly only 3!
I would suggest that whatever has been said about sheepskin is nonsense. It's been a valuable tool for many people and their horses. Remember, what might suit one horse may not suit another.
And yes, many products are produced which I personally wouldn't use and some really shouldn't ever be made. Sadly this is the same in any walk of life not just the equestrian world though.
What girth would you recommend as it is a minefield. The "humane" girths have a metal focus spot and if you lose the strap you have no backup. The traditional girths have a concentrated pressure line down the centre. I have been advised to get a Stubben string one but I have heard bad reports about those too. I quite like the Libby's two part neoprene lined ones but they are quite bulky so anybody buying one may need to go up a size. Also what is your view on girth sleeves?