That's one thing Hasselblad did not do right. The position of the tripod screw socket changed a bit over the years, so not all brackets fit all cameras.
So if possible, return the item.
An L-bracket is not what i would want to be using combined with a 90 degree prism. Your left hand is up high, your left arm 'floating' free in air without your body to lean against.
That, combined with the leverage of a camera not resting on the hand that is holding it makes rather unsteady and uncomfortable handholding, in my opinion.
I don't like L-brackets anyway, for no other reason than that leverage alone: the camera, out on a bracket to the right of the hand that is holding it, is trying to twist your wrist, with you having to counter that constantly to keep the camera level. It's not very nice, and eventually you are going to give in, and let the camera drop a bit.
The original Hasselblad grip, with the camera resting on your hand, is much easier. And more steady.
But to each his own, of course.