valve stem 1800s

I have a VTX 1800 S with 15" spoke rim and I plan to go to the Darkside. I have purchased a Michelin 205-70-15 Hydroedge tire and Dynabeads. I have read you can run the tube or seal the rim. I am not sure which way to go. The sealed rim needs a valve stem and I have read that the valve stem hole needs to be enlarged by a little bit. Does any one know how much a little bit is? What drill size should I use to enlarge the hole if that is the way I decide to go. I have to do this soon my MC tire is slick and it is raining in Houston. The ride to work this morning was was fun but I would really like more grip.

I'm not sure. You might be able to find the stem you want to use and see if they say what size hole is needed. Or I'm sure some one will check in and let us know.
Yesterdays storms were fun.

Jerry