If the short growing season is the problem, why not just start them early, grow them to a good size indoors and then put large plants out early in spring, rather than trying to grow from start to finish indoors? I don't see any reason why you couldn't get good results with a nice start. I'm zone 5 and I get 3+ months of ripe pepper production. 1 foot tall+ plants put out early in spring should have no trouble producing, and there are a lot of people here in zone 4/5 who get good harvests.
I'll run down what I do. You can see a 1 day yield from my 32 superhot plants this year in my post in the welcome forum here
My Welcome Post
I started indoors from seed in early Febuary. Next year I'm moving that to early January based on this year. Seeds are started in nursery trays on heating mats to keep them at 85, plenty of posts on seed starting around. I fertilize with diluted fish emulsion once they get their first true leaves.
I move them to 3 1/2 inch pots at 6-8 weeks. When I transplant I mix an organic starter fertilizer with mycos in the potting mix. I make my own mix, but you can also just buy promix. I try to keep daytime temps in the 80's, and grow under a mix of floros and high pressure sodium lights.
In April they're moved up to 1 gallon nursery pots in still in the pine bark potting mix. I start moving them in and out on nice days.
In Mid to late May they go out for good in 5-7 gallon plack plastic grow bags. Black Plastic is the key for me, as the sun warms the roots much warmer than they would be in the actual soil, and in the containers the roots cool off at night. In the free draining potting mix I use, it's easy to water them the way you want, either trying water restriction to see if it increases pepper heat or ripening or just trying to maximize production. I fertilize with organic ferts every 4 weeks or more often if the plants appear to need it.
At the end of the season you can pull the plant out of the bag, prune the top and the roots and put them back in the 1 gallon nursery pots for overwintering. In the 1 gallon pots they take up less room and you can fit a lot of them on a shelving unit in front of a south facing window with a couple of shop lights for supplimental lighting. Toss the spent potting mix in the compost bin or straight into the garden.
That's it in a nutshell, it works for me. Wash the pots and bags in bleach water to sanitize them and they'll last at least a couple of seasons. Growers Supply Company sells the grow bags for something like 30 cents a piece. Used nursery pots can generally be picked up free or cheap from landscaping companies in the spring if you ask nicely.
Last year my overwintered plants did not make it due to a lack of water when I was away on business, but this year I've bought a drip system and timers so that shouldn't be an issue.
Peppers generally can't stay outside until June and mid September I start having to do the shuffle back and forth to the garage with everything in pots on colder nights. Basically I have to jump through hoops to get decent production here, it took several years to work it out for me. Happy to share what I do if it's a similar situation.
