Hi removing a lot of the blooms will help and I would use a product call super bloom and a growth hormone called giberillic acid if allowed. Give them full sun or at least 10 to 12 hours. I have noticed though that a plants genetic make up has a lot to do with the size of the plant along with the species. I have a rare wild species that can grow to nearly 9ft. tall, but the pods are quite small if you could breed the genes from a very tall plant like Capsicum praetermissum into your pepper you might end up with a very tall plant that has large pods on it. this could take years though.
I would watch how much nitrogen you use to as it will effect the size and amount of peppers you get.
George W. Z5 Mo.

POTA;
FWIW, (For What Its Worth), a LOT of GIANT VEG records come from alaska, where they have almost 24hrs of daylight, coincedence?? I think not. I would think to increase the "light" the plant gets.