Here is a program from U of A that I have found helpful http://soyva.uaex.edu/soyvainput.asp You will notice it is a 09 program and the data would come from 08 and before. After the 09 harvest I'm not sure I'd want to put much stock in that (09) data anyway.

There is other U of A yield data for your part of the state.

The general opinion here (neAR)is that grp 4 soys would have yield advantage planted in twins, however there probably some 4's that bush out enough to plant in 38's. Your also enough south of us to make some difference.

Stein 4782 have been good on this farm.....for what that's worth.

First year after cotton you should have some excelent yields......just watch those diseases and the nematodes as you have mentioned.

John