Just got my Boba 3 G and tried carrying my 25 lb son in front position. To my dismay the straps where really digging in under my arms. I'm a "fluffy" girl lol and have a little extra meat should I try making straps shorter or longer??
It's hard to troubleshoot without seeing but... Buckle carriers can be a bit fiddly in terms of getting the perfect fit - not all carriers are comfy for all wearers. I'd try snugging it up and letting it out a bit (although letting it out runs the risk of him pulling away from you which won't be comfy). You might also try the back carry and see if that's a better fit.
Re: Boba Digging in under my arms
*~PAIF/SAIF welcome and encouraged!~*
Breastfeeding Counselor with Breastfeeding USA
Babywearing Guide ** Newborn Carriers
Cloth Diaper Guide
Safe Bed Sharing Info
unfortunately, I heard this was common problem with the 3G, which is why I went with the Butterfly.
Best suggestion is keep playing with the straps?