Jack...

IFR/IMC flying in sailplanes here in the USA is legal.
FAR 61.57 address carrying passengers only. You must
meet the regulatory requirements, that are....have
an instrument rating airplane & a clearance.

Good common sense and discretionary on what types of
clouds you may encounter is very important as well.

I have an article written on the subject, it is 15
pages....the original Cloud Flying Manual I am putting
together will be over 50 pages.



Shawn