Yeah guess I am a little hard on my self..lol..I'm going to try the dry start method to see if I can get it to grow any better then the ones in my 20l. I didn't have enough aqua soil so I have some dirt under my aqua soil. Not sure if that is a good idea or not, but I'm gonna try it. I would like to have a few fish in it by next summer.
well if you are using aquasoil as in the ADA stuff, i believe can be nutrient rich. i don't have experience with ADA soil but i am guessing at least you'll get all the trace elements your root feeder needs from the clay component of the soil. it may not hurt adding a root tab or other substrate macro (NPK) fertilizers. in your case osmocote could be an affordable option as you are doing a dry start.
emersed setups key to success is the "aerial advantage" plant leaves are exposed to all the oxygen and co2 it needs to metabolize, so you would definately see marked improvement in growth.
the trick with any DSM comes when you flood the tank. two major things to consider is what happens to your soil and what happens to your plants.
in the first instance, people use DSM to avoid algae blooms due to the use of and conversion of terrestial soil to a submerged state. as you are using aquasoil substate, its already in a stable submergable state, so no issue here. if not, would have to do a series of wc to flush excess nutrients released by the soil.
the second instance pertains to the plants... now you have emersed form plants that are being converted back into submersed form. basically going from unlimited O2 and CO2 to asfixiation. so definately CO2 injection or supplementation is required as well as a lightig and wc routine to ease everything back to a submerged state.
unfortunately i don't have successful experience doing this and defer to the other TPT members for their input. good luck!