Those smaller inner buds (lower buds), you were talking about being "airy", that's what the underlighting is for. It will help plump them up & make them tighter. I harvest the top riper buds first & the lower ones aren't far behind with the underlighting, just a matter of days. Or if you prefer, harvest the whole plant, but then I seperate the riper tops (some amber trichs, buts still mostly milky) for pm & save the lower buds (milky, but no amber yet), for am. That way you have 2 different highs from one plant, & keeping them seperate, you don't end up with an 'up' high at bed time, or a sleepy 'down' high early in the day when you have things to do. But definitely underlighting will make those lower buds bigger & tighter. As for the photosynthesis, the leaf is translucent enough for that extra light to reach the photo cells, so yeah. If you try it, you'll like the results.
-- I kinda miss the old days.. 600+ big momas outdoors & 20-30 3 1/2- 4 footers indoors 3X's a year. Kinda crimps the breeding experiments, but too many thieves & snitches to go commercial where I am now, so what would I do with it all? Just one of the many reasons why I find the T5's & cfls so perfect for what we do, sm personal stealth grows.