I've done it many times...it's not ideal but in the absence of fresh cut meat, it works. Over the last couple of years Ive probably turned a dozen or so Walmart butts into various salami with good results. The only time I had a problem, so far, was a walmart pork loin i was trying to make a lonza out of...never firmed up. Discussed it with the sausagedebarchery guys and came to the conclusion it was PSE (pale, soft & exuditive) meat...a common problem with box store meat.
I'd say go for it....and post pics!
Cant comment on the Uami bags....general consesus ive seen is they aren't great for charcuturie...but do a decent job of dry aging beef etc. Again...just hearsay...I dont have any personal experience with them.
PS...what soppresata recipe are you planning on using?