To whomever asked, yes the WnS liner is a bit thinner than the Gerbing, and also more form fitting, so it should fit under your jacket more easily.
Note also that WnS has two versions of the liner. One is breathable, the other blocks the wind. (I think Gen 2 is the breathable version, but double check with them.) The Gen 2 is probably better under winter gear as it won't let perspiration build out underneath. The Gen 3 might be better worn under a mesh jacket.
When I bought my liner (one of the first he sold), I ended up with one that was too big. Mike took it back and sent me a smaller one no questions asked. I paid for shipping back to him, he paid for shipping the new one to me. I also had a dual heat-troller fail after 2 or 3 years of use. Well outside warranty, but Mike replaced it for me no cost. (He even paid the shipping). I also have a perm mounted grip controller, and broke a lead to the blinking LED snaking the wires through my ST. Totally my fault, but Mike hinted at replacing it before I told him I didn't care about the LED. Not saying he'd do this in every case, but he does stand behind his products.
I haven't put the VP rain guards on my 1300 yet, but used them on my 1100 and they were great. No aerodynamic effects that I could notice.