That third cylinder sure makes for a weird-sounding steam locomotive. I probably won't do the 4-12-2. I am running out of parts for the Mantuas. My latest effort has been to just build up a Mikado. I bought a "ready-to-run" chassis for a Mantua 2-8-2, including drivers, a gearbox and a can motor, only to find that the cylinde block was for a Pacific boiler. Happened to have a Mikado block, but that meant reconnecting the valve gear, which has the crosshead guide, crosshead, and valve gear rod that have to be installed in the new block, on both sides virtually simultaneously. PITA!, but got it done. Next, I found that the trailing truck wouldn't swing under the rear of the chassis. Lots of elbow grease with files finally took care of that. The motor has wire leads from the motor, so that there is no contact with the frame (in case I want to put in a decode...not likely to happen right now. Connected the leads to a 9v battery while holding the chassis in my hand. Runs fine. Set the chassis on the track to see which wire should be connected to the frame so the right side drivers would pick up current correctly under DC. DEAD SHORT SOMEWHERE! No, not anything readily apparent. Looked at the drivers. All the left side wheels apparently insulated between hub and tires. On a hunch, I hauled out the multi-meter set to R and checked each wheel on the insulated side. You guessed it. Although you could see the white insulation, the third driver showed the insulation wasn't insulating! All the rest were okay. Back to the parts drawer. Two blind driving wheel sets left! Checked them over. Both okay. Swapped the good one for the bad one, and now everything is okay. Bought a couple of pilots on ebay for Mantua's for $30 each plus shipping. Discovered the ladders are meant for the smaller smokebox of the Pacific or maybe a light mikado. A little work made one of them suitable for the Mike boiler. (Still have to drill .020" holes in the outside risers for the Burlington-like handrails. Probably get the thing finished by this weekend. Now what do I do with it? No room on the layout, and even my basement storage track is running out of room. NOT going to try to sell them on ebay. Maybe at a local swap meet July 15th....
Stay well and safe!