This, I am told, is relatively common Type IV Bus practice. I'm sure that Bob Hoover has something to say on the subject, check
www.type2.com .
It *does* affect the deck height and compression ratio. Heck height changes by the height of the squished metal "gasket", as you might expect. However, CR changes are bigger than I would have thought. On one motor, the difference was about 0.3 points! Just from leaving those rings out.
If you want to be sure of your CR, then you have to measure the volume of your combustion chambers (all of 'em!), the dish on your pistons (if any), etc. Then you can do the math of volume at BDC divided by volume at TDC.
--DD