At the Haywards Heath show I picked up some magnets sold for uncoupling Greenwich couplers. These are of the "rare-earth" (neodymium-iron-boron, I believe) super-strong magnets, similar to those I bought a few months ago but bigger, this time about 5mm diameter by 2.5mm. The idea was to improve the uncoupling magnets on Awngate. As the Microtrains couplings need a magnetic field accross the track it was clear that the magnets would need to be used in pairs, so I set up a piece of track on the workbench and armed with lots of blue-tack and a couple of wagons, started experimenting with them in different positions.
Now these are STRONG magnets, if placed just under the track the wagons shot toward the magnets and up-ended on to their couplers, which stuck to the magnets! Yet spaced apart and well under the track they didn't seem strong enough, what is probably needed is a block of steel between a pair of magnets. Then I thought, well rather that replace the magnets I had already placed under the tracks, why not just increase their magnetism? So I put a pair of the new magnets onto each pair of cupboard-catch magnets, as shown in the photo below. Well, actually I only had enough to do 5 of the 8 magnets, but some worked OK anyway.
The result is surprisingly effective, the magnets are certaily strong enough now - even through the ballast, but not so strong to up-end the wagons! (they can roll toward a magnet if left very close). I wouldn't say all uncoupling problems have been solved - I still need to check all couplings are mounted correctly and well lubricated with graphite - but if things don't uncouple, it's not the fault of the magnets.