Question about Stretching with Force Extension

[awesomenessofme1]

Basically, I'm trying to create a character that can extend their limbs through controlling external physical material. Stretching with Force Extension seems like a good start, but I don't know if the costs should be different. It definitely seems slightly less useful than regular Force Extension, because while the stretched limbs can't cause the user to lose HP, they're solid, and they can be attacked and damaged.