I suspect that you could take some strong, synthetic cord and put a bulky knot in each end of a length about 1.5' long or so. Apply the HDSS dome and seat one end of the knotted cord in the dome recess where the bushing on the HDSS would ordinarily seat. Loop the cord through one or more dumbbell
weight plates and use it like a
hanger.
That way you could start with a couple of pounds and go up slowly and know exactly how much force you are applying each time.