I have had a Stormscope since day 1 on my IVP.  
The first location was a "best guess" without the mapping.  Bad, did not
work.
We then had the skin mapped and put in a 3'x3'copper mesh as a grounding
plane.  It has been great ever since.  

And it is more than useful.  Just last week in the Chicago area it was
telling me I should be on the ground now!  It was right and I did.
Nexrad (from 45 minutes earlier) and the controller were not painting
what was going on.  Even Nexrad from 6-10 minutes earlier would not have
been adequate.  Sunday on the way west from Minneapolis area, the
stormscope kept me safely out of harms way with a reassurance that I was
doing the right thing.  I do want to add Nexrad into the cockpit and
will be looking at OSH next month.

Carl Cadwell, IVP, N25CL