Sorry, I need to elaborate here. My advice on speed alteration is intended to give the user an indication of shadow detail which is only marginally affected by development times. I'd use the time for 3200 which may blow the highlights a little for the slowest speed but given that most users agree as has been stated by Allen that the next higher film speed dev time should be used because D3200 is a low contrast film then even the dev time for 3200 will only increase highlight density a little.
If 1250 to 1600 turns out to give the required shadow detail then the time for 3200 will be close to the right time
I think that Allen has got it right but the OP may need to discover for himself. Unless he experiments he will never know for himself what his right speed is.
The alternative is 9 shots at 800 then 9 at 1250 etc and cutting the film in the dark into four sections and developing separately and with knowledge of leader measurement to frame one and markers on a bench for nine frames this kind of cutting is possible with the loss of one frame at each cut but it is quite an ordeal unless the OP is familiar with and has had experience with such a procedure in the dark.
That degree of experimentation is probably more than I want to delve into using just a little changing bag. But I do appreciate the insight.