Like Iam said, harvest the top, lower the light and finish the bottom, you will get up to 30% more yield doing this and if you keep the plant healthy the lower buds will fatten up
trimming the lower buds does not transfer energy to the top, the plant spends energy fixing where you cut it and stunts growth
I'd have to disagree. As long as you trim the bottom growth prior to flowering, you will see an increase in growth rate (not stretch, but vegetative growth, and bud growth once the time comes) in the remaining branches that are getting optimal light. This is a technique used by many of the breeders, and I think you will find it actually relieves stress. A plant that is trying to produce resin for the top half but still trying to produce weight on the other half is under more stress than a plant that is receiving optimal light to all budsites. You will see that extra 30% in the increased top size due to the increased vigor. Your plants are not harmed by trimming off the bottom, shaded growth. As long as you stay under 1/3 you cause no STRESS, although I will admit you may theoretically loose energy briefly while those areas repair. Is it enough to notice, no. And remember you are doing this to increase the growth rate of the tops, over time the benefits of the increased top growth become clear and outweigh the time etc that is needed to chop the top and flower out the bottom.
Plus, are you really getting a 30% increase in yield by taking extra time flowering the bottom of your plants which by that time have little vigor, so you would be looking at around 2 weeks minimum. I'd be half way through veging my next crop, which is something you may be overlooking. Perpetual growers would be 2 weeks into flowering their next crop.
That brings up another benefit of trimming the bottom before flower, this provide's you with clones to keep or sell.