Thanks Shera, exactly what I was wondering! The hoppers are definitely too small, I just didn't want to overload him feeding little meals too often. But I weighed and calculated everything and it looks like these little hoppers every couple days is roughly equivalent to the 10-15% amount every 5 days.

I've got 2 hopper mice left, in a bag together with a 10 gram rat pup that was considerably smaller than the others. I also rubbed a rat pup on the last hopper mouse he ate to introduce him to the smell, and he took it fine. Next I'll try his first rat with the mouse smell on it

Thanks for the info!