John,
When I first started making risers, I had several "practice" pieces as well. I found a pile of old wood cargo pallets (I seem to find them laying around a lot) and cut my practice risers from them. Around here the pallets are made from oak, ash, sweetgum and other hardwoods. It's a dang shame, to me at least, to cut down these trees for a disposable product, so I guess I am recycling. Most of my practice pieces actually found their way into good bows. The hardwoods in the pallets worked really nice and had good looking grain.
Nab you some hardwood off of some pallets. Good wood, good practice.
OkKeith