I've used EA-40 in a 1:1 ratio in the few bows I've made. Several of those are still operating wonderfully after 20 years. The 2A:1B ratio states it has better heat resistance (not a concern I don't think) and improved properties. Are the improvements applicable to bow performance and for those of you who have used 2:1, is the difference noticeable? Or is it a case of "better" must be better?
The thing about smooth on at least 1-1. Never more hardiner than resin. I always use little more resin. And my hotbox usually gets to 130. Have had only two bows in 20 + year delam. Pretty sure one was a dry fire.
I mix mine closer to 2:1 resin to hardener, and pretty much just eyeball it. With too much hardener it's got a yellow tone to it and the viscosity is thinner. When it's 2:1 or close to it, it mixes up white in color and lays down much nicer with a putty knife. I always spread both surfaces in an even thin coat before going in the form.
Another little trick I use is putting both parts in a paper cup, and pop it in a microwave for 10-15 seconds before mixing it. It mixes much better when it's warm and spreads easily with a putty knife.
I've had really good luck with smooth on over the years with very few issues. But I've never mixed mine 1:1 so I can't compare strength quality.