IIRC, when I actually chronographed the Privi Partizan 85 grain FMJ factory load, it put out somewhere in the neighborhood of 1450 fps (claimed muzzle velocity was 1722 fps out of a 9.84!? inch barrel).
The S&B factory load of the same weight was around 1575 fps (claimed muzzle velocity was 1647 fps from a 4.72 inch barrel ). The only really significant difference between the two loads was in how far the brass was thrown and how beat up the cases were. Most of the actual mil surp 7.62x25 ammo (including some 1962 Romanian) that I've run over the screens gives velocities of around 1450 fps as well.
http://gunlore.awardspace.info/rifledarms/ammunition/surplusammo.htm
The point of all this, is that these pistols, whether Tok or CZ are OLD. Most of them probably haven't been inspected or serviced by a trained armorer in 40 or more years. To expect these old weapons to safely handle loads well in excess of what their respective militaries asked of them when brand new is, in my opinion, unwise. It's not as if the military men and ballistic experts of the Eastern Bloc didn't know that they could get increased velocity, penetration and killing power by adding more powder to the case, theirs was a deadly serious business. There must have been a reason that everyone pretty much kept their velocity and pressure levels fairly close to 7.63 Mauser specs and it probably wasn't because they planned on using the ammunition in huge numbers of captured Mauser Broomhandles.
You say that you can't imagine why it would be any more difficult to safely load 7.62x25 sabot rounds than doing so in a 30-06, so let's leave imagination out of it and talk facts.
1 - 30-06s are generally fired from rifles with strong, multi lug, rotating bolt or falling block single shot actions. These actions are several times as strong as those on a Tok or a CZ.
2 - The chamber walls on 30-06s are, by and large, much thicker and stronger than those of the aforementioned pistols.
3 - 30-06 brass is thicker and has a much stronger head than Tok brass.
4 - The difference in case capacity is huge. A few tenths of a grain overcharge in a 30-06 case with a 55 grain bullet and 5.7 grain sabot probably wouldn't even be noticed. In the little 7.62x25 case, with a much larger proportion of the internal volume taken up by the sabot and a thinner, weaker case wall, a very small increase in charge weight can run pressures up to dangerous levels with no warning.
Please understand that I didn't spend the time typing this up because I want to spoil your fun. When I saw that you were considering loading 7.62x25 sabot rounds without even having access to a chronograph, I became seriously concerned for your safety. At one time I loaded quite a few of them myself, reaching velocity levels that were quite impressive. I was lucky and still have all of the eyes, fingers and teeth that God gave me, you might not be that lucky.
Remember:
There are lots of bold handloaders.
There are lots of old handloaders.
There are very few old, bold handloaders (and a darn sight fewer that have all of their original parts intact).
Have fun, but more importantly, Stay Safe,
Swampman