>>/81292/
I have 502 which has a completely useless velcro strip in addition to the boa which seriously does nothing all. It has no function it does not tighten anything up or hold anything in place. 503 doesn't have that so they are definitely better but I ain't pigging nothing new these shoes are fine.
That being said don't sell yourself short you're not that far off and you're going to reach 380w by the end of the year we calculated that months ago 
 >>/81294/
I don't see what you would need a second boa for tbh, the shoes are perfectly tight with just one and boas stick out like gross tumors from the shoes so the less boa the better imo