What you need to do is not focus on Twins or a Quebbler Suit. I can't even begin to explain how broken that is. Sorry, not trying to be rude, it's just the truth. Twins are not a primary weapon, and no shield combo bonus is gonna change that.
If you're playing Fg then your best talents are Rifle and Grenade, both used mainly to kill bosses. The Fg Shotgun is strong but much slower than a Gunmaster's, same goes for Laser. Maybe Grenade PA+5 with Grenade Critical 2, Rifle PA+1, Shotgun PA+1, and Spear PA+1 is a decent Fg setup. There's really not much use in raising the Laser PA because it's just too slow, you can't use it the same way a Gm does.
But if you're playing Fg simply because you bought a Quebbler thinking you'd totally pwn Seed with it, then sell it and the Amphis, forget it all ever happened and go back to Gm lol The Kevlar Suit's main focus was the amazing rifle and shotty combo, not the twins.