Where are big catfish in Idaho?

I have only caught catfish out of Park Center pond (Average ~2-3lbs) and near Brownlee Reservoir off of the shore (Average ~2-4lbs). I really want to catch some bigger cats this year. I have not had any luck on the Snake river at Swan Falls or Snake River near Homedale fishing by the boat launch. I have heard of people pulling in bigger cats (10+lbs) from Swan Falls... are they doing overnights there to do this? Peak hours when I have caught 6 cats in a night were from 10p-4a.

When I bring home trout I tend to fillet them leaving some waste. Can I use the head or any other part as catfish bait?

I know in some states, using any part of a game fish as bait is illegal. I also know that trout must be killed when removed from the water where they were harvested. I just hate wasting the head and tails of trout carcasses if I could be using them to catch catfish. Thank you.