At BlueMountain (where we did most of the work on Deedle), they actually had a utility for passing data to Excel. We wanted to include this in Deedle, but never managed to publish it, because it would take some time to polish & document things.
We actually put the source code on GitHub (as part of one of my demo talks), so you can get it here.
Using this, you should be able to just write:
xl?A1 <- deedleFrame
There is a lot more you can do - have a look at the members of the Xl
type.
Also, we originally used NetOffice which is an easier to use wrapper for the Excel COM interop - the referenced sample is not using it, but it is probably a good idea.