Bottom watering by floating?

I checked my onion seedlings this morning that I gave the haircut to yesterday, and noticed the trays were REALLY light. I think the fan I started running sped up water evaporaton. They definitely needed watering (last time was Wednesday evening when feeding them.) I always bottom water, but it seems to take a long time to wick up in my trays. I was putting in about 1" of water in the bottom tray and letting it wick up into the cell packs for as long as it took (several minutes at least, sometimes up to 20 minutes before the surface color started to change and the packs felt heavier.)

So this time, I took a taller tupperware container, put fully 2" of water in it, and then for each (2 inch deep) 6-pack, put it in the water. The tray floated on top of the water for a few seconds and then slowly would sink. Within 20-30 seconds I picked it up, let any excess water drip out the bottom, and then went on to the next 6-pack of cells. My 8 six packs of onion seedings were all watered wthin less than 5 minutes, going from really lightweight to feeling reasonably heavy (about the weight I recall when first planted in moistened mix.)

Has anyone else tried "floating" the cellpacks to bottom water like this? If so, is there any experience here on whether it has any drawbacks?

Thanks,

-Ed

Sounds like it works well, except for the time spent watching the plants in the cells bob around.