I've had both the 3/8" and the 5/8" and prefer the latter. It's not "too springy" at all...quite comfortable and reasonably durable. Easy to cut to fit around stuff, too. One of the reasons I suggested the roll for you is you're starting from scratch and you can really end up with a comfortable floor by having most of it covered with the mat. I'd only leave it off wherever you might spray finishes...or have a removable section in that area for obvious reasons. It will wear a bit over time from abrasion, but I don't find that to be a big deal in the shop. In fact, I use this same material in our kitchen over the brick floor to line the "galley" where we stand to cook, etc. When that gets worn too noticeably, it goes out to the shop and a new one goes in the house. (like every 5 years or so)
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The most expensive tool is the one you buy "cheaply" and often...