Funny you should mention this.....
I use .030" glass for kid's bows and, generally, anything I build under 30 pounds draw. I just put together my short pattern recurve #3 and I'm thinking this one is going to come in closer to 40#. I used a strip of Stabilcore in it as well.
I think it will be ok. There seem to be a lot of competing theories about the percentage of glass in the total stack. Truthfully, I think longbows are less sensitive than recurves to that percentage. I think the only bad thing which is likely to happen is that the bow might take a bit of set. The potential upside is it may be a little faster due to reduced limb mass.
My personal criteria for determining thickness of glass is based on the desired weight.
I use .030" for anything 30# or less. .040" for 31-50ish pounds, and .050" for anything above that.