Good news! I sent in a request via the contact form at www.marcel-jurca.com and got a nice response back from webmaster Patrick Cottereau including a scan of the relevant page from the MJ-2 Tempête plans. I don't want to repost that here without permission, so I will describe it. In short, the Jurca spade grip shape is an isosceles triangle with rounded ends made from 3/4" x 0.35" steel tubing or 3/4" x 0.65" aluminum tubing (or cast from light alloy). Basically, draw a box about 5 1/8" (130 mm) wide and 6 5/16" (160 mm) high. Then draw three 1 13/16" (46 mm) radius circles inside the box, one each in the bottom corners touching the bottom and one side each and one touching the top along the centerline. Then draw tangent lines from the top circle down to each of the bottom ones, with the bottom of the box already forming a tangent line at the bottom. This describes the outer edge of the grip, which is attached to the control stick canted 20 degrees forward in the neutral position. I could definitely see something like this with a nice leather wrap or cover making a great pseudo-vintage addition to any homebuilt. By all accounts, the grip shape and forward cant make for a very comfortable grip for either hand.