Yep Steve, below the cutting blade and as you rightly say, it opens the gap a tad. I agree with your views on £160 worth of razor needing a shim to get it right. However, imagine this scenario: you've lusted after one of these beauties for a long time, you think the aesthetics of it are simply gorgeous and you just can't imagine yourself having any other. You even love the stand and the whole package is your absolute ideal so your order it in eager anticipation. It arrives and after several weeks, try as you might, you just can't get it to shave close enough despite your good technique so you contemplate selling it and switch to using another razor. However, every time you enter the bathroom, there she is gleaming at you in her stainless steel sleekness with those looks you just love. You so want this razor to work because of the amount of money it cost but more because you find it the ne plus ultra in the beauty department. You resign yourself dejectedly to posting an advert in BST then someone tells you of a free modification that won't ruin the razor and is as easy to do as kiss your hand. A shim! You try it and it gives great results so you feel your £160 well spent rather than a loss in waiting. A few months pass and although you start to feel that it its too much money for a razor that needs a shim, you still love the looks and the shave is now great. Others may not agree with you but ultimately you're happy.
I've read on another forum although I forget which, of one guy who loved the look of his Feather but sold it because it was just too mild for him. Months later he heard of the shimming idea and wished he'd kept his and tried it. Maybe it would have been ideal, maybe not.
Tried shimming the Rocket HD today but to no avail, still not close enough and an irritated neck. I'm definitely in the minority here as most folks consider this a great shaver and I definitely lusted after one. Perhaps my technique needs a lot of work with this razor but as others suit me so much more, I'll cut my losses and try to move it on.
The long-haired Sergeant Major is demanding I cut down to two razors but Im campaigning to keep three. So far the two definite keepers are the Jagger with JEC handle plus shim and the Gillette #77 sans shim. I quite like my ER 1912 but obviously it takes different blades; the big aluminium U guard Myatt shaves really well with no shim but is a pain to jam a blade into; the Old type is a nice shaver but I have to fiddle with the blade to get it evenly exposed each side. Right now, the Old type is winning out.....but that could change.