I have used bagster tank covers for last 8 yrs on several bikes...never had any issue with them. They do come up now and again on ebay second hand. The bagster bags are good too, and loads are on ebay. I cant get find any second hand for my GS ...new is £108
...but bmw tankbags are orrible...so may stump up for one.
Havent noticed any marks on frame paint btw, mine are black rails on the fazer.There is a trade off of looks vs tank protection , paint looks better than vinyl any day. But my 04 silver tank looks brand new after 4 yrs of baglux cover on it !
TBH I wouldnt be without it...