This guy is an idiot.
If you break off the aperture lever, you just halved the value of your lens, which, incidentally, is way more than $200 (try $500-$800 - he must be thinking of the Pentax-M, which is a different lens). Also, the "useless" plastic ring in the back is a matte baffle to control reflections off the silvered parts of teh back of the lens into the mirror box. Finally the fact that he is surprised that removing the ball detent allows for clickless operation shows that he knows absollutely nothing about lens construction. This is the way that about 95% of lenses that are declicked for video are modified. One of the simplest and most well-known lens mods there is!
If you want to use this on FF EOS, buy a set of JIS screwdrivers (so you don't strip the screws, which aren't Philips), and remove the baffle and aperture lever. It is not difficult and can be done in about 2 minutes by anyone moderately competent in lens repair. If you are serious about image quality, replace the baffle with aother piece of matte material, e.g. a small piece of black velvet. And save those parts! If you ever choose to resell, you will be glad that you didn't mutilate your RARE lens as the author of this article suggests you do.
Also, the author's surprise that there are good Pentax lenses out there shows he knows nothing about vintage glass. Pentax has ALWAYS been the gold standard for Japanese primes, before and after their collaboration with Zeiss, and ther independent designs hold their own with the best of German glass. Note that it was Zeiss who wanted the secret to Pentax's SMC coatings, not the other way around!
