Luckily there are some innovative products which adds insulation but not bulk to important areas such as your shoulders. SeasonFive’s Tech Arm Sleeve is just an arm sleeve which can go under your wet or dry suit without chaffing or adding bulk to your shoulder. The sleeve is windproof and has a touch of insulation so can be added to the exterior as well. I tend to wear out my right elbow on wetsuits so the arm sleeve helps keep water out in that area.
SeasonFive also has a Tech Leg Sleeve as well. You can find the sleeves at REI, surf and SUP shops and some bicycle shops