Have I overdone the secondary bevel on this chisel?

[thetyreman]

the thing with sellers is you actually have to do it and try it to know whether it will work, it certainly works for me and all my tools are razor sharp, stick to a method you are happy with and try not to change it.

 

[hughcollier]

I suppose the other thing - now that I am thinking it through (please, someone correct if I'm wrong) - is that it's more important to have a completely flat stone when using a honing guide v freehand?

If the stone is dished and the wheel is referencing off a hollow spot, then the angle at the tip of the chisel is going to be slightly different. It seems like this would be less of an issue freehand as you could kinda follow any undulations in the stone as you go.

I only ask because after regrinding a 25° bevel on three chisels I now have some serious flattening to do on the stones, despite trying to use the whole surface equally.

 

[Jacob]

.....

I only ask because after regrinding a 25° bevel on three chisels I now have some serious flattening to do on the stones, despite trying to use the whole surface equally.

You've hit on one of the main reason for not using a jig. The stone needs not only to be flat but the tool edge itself has to be set precisely to it.
But the top reason remains that you can't put any force into sharpening with a jig - it takes longer and is a finger cramping fiddle.
A dished or hollowed stone is no prob freehand (within reason) and you never need to flatten them. Handy to spread the load though - to keep them flattish as far as possible.
Also you can't easily put in a camber with a jig and a flat stone - all planes work much better with a camber, with one or two exceptions.