I will have to give this a try. I also use the EMT tubing but with 1-1/2" angle iron welded to it. I'm thinking the rebar would be a lot better (easier to sink) in dry ground, not so sure if it will resist being pulled over in the mud.
Not a big deal if you'll always be around when your lines are out, but something pulled my 10' spinning rod with 65# braid and a shad head down to about 20 degrees above horizontal overnight one night. That's with 1-1/2" angle iron 16" deep into the mud. When I leave my rods unattended in holders (in the backyard) I now safety them in with a piece of strap and a tent stake.