I tried GPP for the first time last season. A friend had actually given me a couple of bags and wanted me to "test" it. I had an area to plant it but one that had not really been limed and fertilized and hahad never really been planted in the past, it was simply old pasture. Welll, I applied RR and then I plowed the area, I then disced the plot and then broadcast the seed and then using a used a drag to firm the seedbaed. Despite a very dry season the GPP came up nicely and produced some decent sized turnips by hunting season. Overall I was pretty impressed with the plot but still find RR soybeans with brassica broadcasted among it to be a FAR more attractive draw for hunting season. Good luck with whatever you decide.
Here's my GPP plot on 10/22 after a 9/02 planting date.
