Rb compendium question

As part of the remedy for my latest attack of G.A.S. I bought a compendium shade on the auction site.
It arrived today and I scampered to my camera bag to attach it so I could sit back and admire it. It falls off. Damn!
Turns out the inside diameter is .115 in. larger than the outside diameter of my 90mm (non C) lens.
What is the reason for this discrepancy? Does the O.D. of RB lenses vary? Are there different shades?
I own a lathe and I can easily make a split ring to solve the problem but I really hope I dont' have to make a bunch of different rings as I acquire more lenses.
Does anyone have more info?
thanks,
Larry

the hood should've come with a mounting ring that screws on to the 77mm filter ring on your lens.

Yep, your just missing a part. I had a third party shade that came with my original RB kit. It didnt use a mounting ring, just a thumb screw onto the lens. Messed up the finish on the lenses big time so I sold the shade.

Thanks for the responses guys.
I'll see if the seller still has it and if not I guess I'll have to make one.
thanks again,
Larry

Otherwise you could go to your local camera store and see if they have Cokin filters.
Get a 77mm ring and see if it fits.

I have the same problem with a copendicum that I bought of ebay, it came with a 67mm ring, will see what to do when I am in Holland again.

Peter

KEH has a couple of these rings in stock. For the price, it might be worth it over making one.

Hi Ed,
Thanks for the tip.
You're right about the low cost making the make/buy analysis sort of a no brainer. Even though it's a relatively simple task, by the time I measure, sketch, scrounge a piece of aluminum from my junk pile, set up the machine and recall how to single point metric threads I'll have at least a couple of hours (or more) in it. That's if I don't scrap one or two or cut my fingers off.
It's just that I've been trying so hard to avoid that doggone KEH place. It's like offering a big bag of dope to a junkie.
Guess I better spend the twelve bucks. And while I'm at it I'd better order the gel holder too. And I've really been wanting.... Nooooo! Someone help me!, It's an attack of ANAL!
thanks again for the tip,

Larry