It's been a long time since I've had the time and inclination to work on my model railway. However I recently been working on coupling design for Holloway Goods.
Mr Peco's nuts are used to hold the wagon body to the chassis, with the weight, held in position, between them. This method is better then glueing because it allows the components to easily be disassembled if required!
My design criteria are that the train should be able to negotiate a 75mm radius curve reliably without derailing. The actual minimum radius will be 90mm, but if the above condition is meet, then I shall have no problems on the actual layout.
The picture above, was taken on a friends micro layout, which has 75mm curves to minimise the area taken by the fiddleyard.
I have no objection to the coupling system being single ended, that is to say different couplings on each end of vehicles. In this project I kept the peco coupling on one end, but I have filled the thickness down to half the original. I tested a coupling to see if it remained coupled and it passed the test. The thinner coupling is less obtrusive, then the original.
The other coupling is replaced with a simple hook, made from stainless steel G String, purchased from the local music shop.
The front angle of the hook is about 60 degrees, it is important that there is sufficient gap to allow the modified Peco hook to drop under it's own weight, even when a magnetic dropper is added.
I wanted the train, composed of loose coupled wagons, to close up when the train comes to a stop, say at a signal, and open up as the train started again.