Microbiologically speaking, a vector is what carries a pathogen from one host to another. Any highly porous or fiberous material (ie. neoprene or felt) would serve well as a vector for didymo and other organisms. If you're concerned about serving as a vector for invasive species or pathogens, wash your gear in hot soapy water after each use. The surfactant action of soap and a light scrub are usually sufficient to dislodge most micro-organisms.-dirty equipment transmits vectors; not felt
I can get equipment looking very clean with a high pressure wash. I don't think my cleaned felts are going to carry more vectors than someone's dirty rubber soles.
I used their extreme model before that pic on my felts...still can only wade some spots on the T. others it's shoreline only for the most part...cleats don't fit...wading staff would help but I don't dig them...i just walked in from spending the last two hours on the lower big hole with the studded vibram soles. Overall i was impressed, and although a short sample time, i would say as good as felt. as good as felt with studs? i don't know. I put the studs in a similar pattern to the "extreme" setup in this link. http://www.flyfishusa.com/apparel/stud-service.html
Simms L2 wading boots are narrower than the rest of their boots. These boots were discontinued several years ago yet I still see unused pairs these boots regularly offered on ebay at some very attractive prices. I owed a pair once and they served me well.When I was in my 20's, a long time ago, I couldn't afford real wading shoes, so just took a pair of high top tennies and glued some carpet to the soles. Worked fine! I'm not concerned about running out of felt, since there's always carpet around, but a good cleaning and bleach, along with drying in the sun, should eliminate any transfer problems, don't you think?
I worry more about not being able to find a pair of narrow boots once my Borgers wear out. Does anybody make a narrow-lasted wading shoe?