Obvioulsy, I know nothing about your area, but, let me tell you what seems to work well here.  Plant into the live cover crop.  If the ground is fit to spray it, why not plant it first and spray later?  Or set up planter to spray at the same time?  The second school of thought is to use gramoxone to lessen the time between spraying and crispy dead cover crop so that you can plant much sooner.  To hope for dry, warm weather for two weeks after spraying glyphosate is most often a pipe dream here and I can only imagine that it is the same for you.  I don't know what to say about your experience with the live cover and drying.  A live plant is certainly pulling moisture from the ground where as dead plants aren't.  Perhaps the surface is damp, but, I can't imagine that the soil profile is wetter??  Not trying to convince you otherwise, just thinking out loud. 

Brian