Hello,
I dismantled the loco down to the frame for the changes on the chassis.
Once the wheelsets are removed, I took a closer look to the frame. You can barely see some marks on the frame, where the axlebearing will be located after the modification.

Now comes the hard part - I cut the new slot into the frame. As it's made from steel, I used an angle grinder for rough cutting and finally filled the slot to proper dimensions. Be carefull to get a proper slide fit for the axle bearing. You have to file away a few millimeters of the firebox-sheet on the inside as well to make space for the lip of the axle bearing.

The steel frame is rigged enough and will keep the axle right in place. If you like, you might add a piece of material to the rear end of the new slot to close the gap, but it's not needed to keep the bearing in place. Once the springs and lower bearing lock are in place, the bearing will suspend and work as before, just on the new location.

I closed the old slot with the original bearing locks and made new ones for the new location.
Last step is to shorten the connection rods. I determined the correct length first and used a lap joint and silversolder to reconnect the halfs of the rod. It still needs some finishing.

And here we are - A 2-6-0 chassis with shortened wheelbase.

Next is to reinstall the brake detail, adding some brake cylinders at the rear and installing a Kadee coupler to the pilot.
Gerd