Welcome to the forum Ed and congrats on acquiring Vernon the BP. Hopper mice do seem a bit small so I'd go with offering two each week and using up the four you have on hand then going to a nice adult mouse once per week till your BP is ready for more. To feed multiples just offer the first as you normally do and once your snake has it down into it's body cavity offer the next one nicely warmed up as well. Sometimes they get a bit confused having a second prey offered so you might have to do the zombie mouse dance on the tongs to encourage the strike on the second prey. Usually though if they are hungry it doesn't take much encouragement LOL.