I am going to have to use magnets to uncouple on some areas of my layout where I cannot reach. Is there any rule of thumb concerning where to place the magnet?

I know from experience that unexpected uncoupling can be a problem and I would like to avoid that if possible.

Since my last blog entry I have tweaked and tuned (and added guard rails to) the double cross-over until it seems to be happy.  I had trouble running steam through it - I think because of too tight flangeways - so I broke my rules and bought a diesel.  It's a sweet-running Atlas MP 15DC (n scale DCC).  I may convert to diesels permanently.  It is a lot more comfortable on my cross-over than the steamers and is very smooth in switching.

Ok, an overview is in order. I like the new design as it serves "an end point" for a single track railroad which is 30 inches wide and covers an "S" curved railroad extending to 20 feet to the other end (a port and small yard area). A diesel switch engine serves each end and  2-8-0's with a max of 6 cars or so run from end to end. There are no interchange tracks and the railroad doesn't serve as a feeder to any other road. It's just for me. . .

The fireman side valve gear crank leans towards the cab, when it should lean to the front when the rods are down.  Has any one been able to fix this?  These engines look and run great, but this detail ruins a great loco.