John the dustcover rule is not aimed at the CZ Shadow. Thr rule was in place before the Shadow was produced. The whole concept is to try to maintain the sport for relatively inexpensive stock pistols. SSP Division is for stock guns and there is a weight rule as you know. If you can get the Shadow down to make weight it is good to go. The SP-01 was ruled to be a variant of the 75B, a good number of the parts are interchangeable thus the dust cover was a modification of the original design so it has to make weight in SSP, where full length dustcovers are legal, in order for it to be able to play in ESP.
The idea is to give the shooter as many places to play without having to go out and buy another pistol. So it isn't "Nuts" nor is it inconsistent with the concept of IDPA.
As far as extended mag releases are concerned if the gun comes with an extended mag release like a couple of the Glocks for instance and the Shadow, if the latter makes weight, you are presently good to go. In ESP/CDP extended mag releases are allowed provided they do not extend beyond .2".
There are only five pages in the rule book describing each division and what is allowed or not. All you have to do is decide whcih division you want to play in and find a pistol that meet the criteria for the division you choose.
Take Care
Bob
PS As an aside I should add I may change out the extended stock mag release on my Shadow with a 75B mag release. I have to leave the mag release on the left side in order to for the .22LR mags to seat when I use the .22LR top end. I prefer it on the right side as you know. When I reverse the mag release to the right side it sticks out to far for me and it is uncomfortable to depress with the trigger finger.