your plants are still young. Obesums left under ground will change into bigger roots in time. The root mass you have now will grow. I have plants that have been underground for 3 years. I am leaving them till Spring. They look so gnarly now. Almost ready to raise.
I would not be able to prune now because I live in the mountains which cool off faster in early fall. I will be cold in a month and 1/2. Where you live you do have some time before you cool. You would not see much growth above but might have more below. It is up to you. Did your plants come bare root? This can put them in shock for a bit and slow things down. I have even had plants I got shipped in pots go into shock. You have similar weather to Kens so this may not happen. My tree came from the south with high humidity to my 15% humidity. All plant action depends on your weather. This things are tough. You won't have super fast growth like you would in Spring. But you can try it. The heat and lights will help keep things growing. but you may still not see a lot till Spring. Do you know where you want to cut? You need to have a few old leaf nodes below the cut. You can seal the cuts with cuts with Elmers waterproof wood glue. It help the would look better.
If you do plant on Trimming. We can help if you give us a close up pic of how low you want it. Get it back in the sun as soon as the glue dries. The heat and sun will help push it to grow for as long as it is there. I have my smaller plants on a heat pad.during the winter because it is not as warm as the plant loves. So winter window light, solar light bulb. heat pad are some of your options. Let us know if you prune or not.
