seeds, rapid rooter to rdwc?

So I've got some seeds started in rapid rooter plugs and they are about 4" tall with about a 1.5" tail hanging out of the plug.

I have each one in a water bottle cut in half and put back together like a elementary green house ha.

How long till I move them to the system and start top feeding?

Also I'm concerned with top feeding these plugs will retain too much moisture and give me stem rot since these things retain water like a sponge... any suggestions or am I over thinking it