A few years ago I got a non owners policy through the
EAA. The company doing this for EAA is Falcon Insurance
Inc in Kerrville, TX. The policy covered experimental
powered aircraft but NOT experimental gliders. The
underwriter is Global AAU. After some research I recently
changed my non owners policy to one associated with
AOPA. The underwriter is AIG and I specifically asked
the broker to check that experimental gliders would
be covered and they looked into it, got back to me,
and said yes, experimental gliders ARE covered. Also,
if you are a member of AOPA you get a discount and
the insurance is the least expensive I have found so
far. The broker for the AOPA associated non owners
insurance is: Aviation Insurance Resources, LLC P.O.
Box 32 Frederick Municipal Airport Frederick, MD. 21705
TOLL FREE 1-877-247-7767 FAX 1-301-682-9793. Additionally,
this is what it says at the beginning of the application
form: 'Personal Renter – This application is for your
personal and business related use of non-owned, fixed
wing, non-pressurized, land aircraft having a non-turbine
single engine of 450 horsepower or less (including
non-powered sailplanes) and a capacity of no more than
seven (7) total passengers and / or seats and having
a Standard, Experimental, Restricted or Light Sport
airworthiness certificate.'

Unless they are outright lying to me this should provide
the coverage you need.

JLH