I love Sam splints not becasue they are perfect for big injuries but becasue they are even better for small ones. A lot of injuries that are common among my friends while kayaking, camping and hiking are small parts related. Jamed/broken fingers and toes can be treated with improvised splints but there is nothing that can substitute for SAM splint and a pair of shears. You can create caddies for an injured part, you can make them into different shapes.
And you don't have to roll it either. Just bend it to the shape of something (canteen, bottom of the pack). I just take with me one small sheet that fits in the back/front of my canteen (U shape folded). So far I used it for a broken finger, toe and for a broken wrist.
Matt