Totally Tubular TT300 behind some sort of toothed closing wheel is the best and safest method for putting down significant amounts of fertilizer with the planter in my experience. Been done for years in the Dakotas and w MN.

One of  the problems with putting starter in furrow is getting an absolutely uniform flow to each row on a wide planter. Putting fertilizer in furrow, there is a very fine line between putting enough on to do some good and damaging the seed. That line also varies by soil type and moisture at and after planting.

The TT300 gives you a bit of a cushion on row to row distribution and let's you put enough on to make it worth the trouble..