[Need help] Trying to make upper arm armor?

[demonwars]

I'm in no way a weight lifter but every time i make a piece of armor that wraps around my biceps it's too loose if i let my arm down by my side and if i raise it it's too tight.

I'm trying to design a retention system with elastic bands to keep it tight but i'm not getting alot closer without alot of resources.
Have any of you had this issue?
If so please tell me how to improve this!

 

[PerniciousDuke]

Have you considered upholstery foam?
demonwars

Hot glue the entire inner bicep with that foam and it will grip your arm, but won't apply too much pressure as you move. It is hot though. If heat is an issue consider placing chucks of it strategically like pressure points to keep the armor from moving.