The balloon jump was, indeed, a bit alarming!! We didn't have reserves when we were inveigled into having a go. To avoid the flailing arms which were likely, we were required to grasp the appropriate trouser leg with one hand and grab that wrist with the other. - (from memory, right leg for a port exit and left for starboard.) With reserves. I understand, the arms are held on top of the reserve. Any way, we made our descents wearing our flying suits , (NEVER again!) - 2 weeks later there were still the unmistakable imprints of a hand grip on the leg of mine!! To be fair, the adrenaline 'high' and the exhilaration of the short period following 'chute' opening were unique rewards!