You have to run it on a sled to get the thinner stuff, and actually, .125 is a little thin to run through by itself anyway. What you need to do is get a perfectly flat piece of hardwood, say oak, and run your lams on that. Just make sure you joint and plane the sled perfectly flat, as any undulations will cause your lam to be thick/thin in areas. The same idea works for tapers. Probably the easiest way is to order a couple taper lams like you want, and sandwich them between a couple pieces of perfectly flat hardwood, making a sled that has the exact rate of taper that you want.
Hope that made sense!