Certain areas do require padding- elbows, knees, neck, helm, kidneys, wrist. Hard over soft. (steel over gambeson sort of thing) Beyond those areas you are not really required to use padding. Check your kingdom's requirements for anything beyond the SCA minimums.
A practice I picked up from war practice, for Estrella XX., was a hooded sweastshirt. I saw Master Ivan wearing one and decided it was a great way to wear padding, but it also has the hood to use as a coif. Just MHO.
In particular I'm planing on making some splinted arms (plastic splints), do I need to place some padding underneath the upper rearbrace and vambraces, or just around the elbow?
grendal wrote:In particular I'm planing on making some splinted arms (plastic splints), do I need to place some padding underneath the upper rearbrace and vambraces, or just around the elbow?
Grendal
You don't have to, but you may want to put a little something under them (I always found a layer of cloth (like my pants) to be sufficient) to keep things from chafing against your bare skin, but not everybody does that.