if in doubt: http://www.digitaltruth.com/devchart.html

It gives 400 times for a couple of developers at various concentrations.

Dont' stress too much - worst case, at 200 it would only be a stop under, which would still be printable.

Personally I'd probably look at the digitaltruth table, look at the times I had for my regualr developer, then end up using my regular dev at the 200 speed plus another minute or two.

OK it's not very scientific, but 200 + a bit extra is probably going to land you within half a stop either way. Thats probably more accurate than I can meter reliably (or more accurate than the shutter speeds on half my cameras!).

Sure someone else can give more specific advice.