I've had the pleasure of speaking with Einar Enevoldson (the man
behind the Perlan Project), and watching his presentations on the
subject.

They used pressure suits during Phase 1 (when they went to 50,000+
feet in a highly modified DG-505).

It turns out that the suits caused all kinds of problems - not the
least of which was controllability; since the pressure suits inflate
with altitude, and that crowds the stick between one's legs (they had
some near-mishaps when pressure suits would malfunction and suddenly
inflate fully - locking the control stick in one position). Plus, the
power and pressurized gasses required for the suits added a bunch of
weight and bulk to the aircraft - and gliders aren't known for their
baggage areas!

In the end, it was determined that a pressurized double-hull (a la
SpaceShipOne) was the way to go. And Einar has flown all kinds of
experimental aircraft over a long career that spans the globe - he's
done the research and has the experience! If you ever get a chance to
see him speak, you should - he's a very engaging person and has plenty
of great stories.
(side note: Speaking of SpaceShipOne, Einar flew a highly modified
Schweizer that could descend in a similar manner to the "feathering"
that SSO does... coincidence?)

Take care,

--Noel