No matter what he did, Sam couldn't permanently hurt Steve in this position, so he didn't care if Sam let got - a little or a lot. Not when he heard the tone of Sam's voice and felt the way he was grabbing Steve like a lifeline. It made Steve feel even hotter - and it made him want to make sure they finished together, or at least crossed the finish line relatively close. So even though it was what Sam already wanted, Steve started speeding up, pushing harder, pushing himself toward a second climax as his fingers kept working Sam, squeezing a little harder (but not hard enough to hurt, and definitely not hard enough to stave off an orgasm, that would defeat the point). He sure hoped Stark had made this bed sturdy, because Steve might have ended up damaging a few, in a couple of low-rate motels, when he and Sam were on the trail of the Winter Soldier.