D
Hi
The Shadow weighs in stock at 41.1 oz with a mag inserted.
The SP-O1 weighs in at 39.6 oz.with a mag inserted.
While the frames are identical, or nearly so, the SP-01 slide and frame have a cut out for the firing pin block while the Shadow does not. This accounts for the majority of the weight difference.
The SP-01 can be made legal by changing the grips to Dennis Marshall wooden grips which brings the weight down to 38.4 oz. and the gun becomes legal for IDPA SSP, thence ESP if the shooter chooses to start cocked and locked.
One of the quirks in our rules allows CZ USA, a wholly owned sub of CZ UB to import the SP-O1 into the US, remove the firing pin block (Done by the "factory"), and sell the gun as the SP-O1 Custom. I should add they also they change the sights and do a trigger job on the gun. The CZ SP-O1Custom is legal to be shot in USPSA but not IPSC I believe. It is legal for IDPA.
Joe T. in Calgary has had his and his son's Shadow worked on by Mathew Mink in the US and Mathew has got the weight down to under 39oz legally. Joe intends to let me know how they shed the remaining .2oz when he receives the gun back from Mathew.
Until then I will be shooting the SP-O1 in SSP and the Shadow in IPSC PRoduction. The SP-O1 has night sights on it presently but those will go for the competition sights used by the Shadow (Maybe save some weight -

)
I am told both guns are made the same way. The frames are not identical though as they come from different production runs judging from the date of manufacture. The Shadow is undercut more by the back of the trigger guard and the grip ahead of the beavertail is cut deeper on the Shadow.
Take Care
Bob
ps One option open to me is to window the mags. I would rather not but may have to if I want to use the gun in IDPA.