I thank you both for your comments.
Now what concerns the usage of the parachute and the type of glider; we are considering buying these parachutes for our club, as our current ones our approaching their end of life.
So these parachutes should fit for both upright as reclined seatings, max top speed of 280 km/hour, and limited spacings between canopy and head. No ballistic recovery system are installed on our club gliders.
So basicly, the parachute should be as thin as possible, and must carry approximately a max weight of 115 kilograms (as this is the current max we target)
We thought of the TSE chute (for gliders) because our current rigger recommended this chute. The ATL's are considered because of positive real life usage by a belgian pilot last summer and we can have them at a relative cheap price.