Yes, I must admit I am aware that even two holiday weekend passenger trains meeting at an M&GN loop was an interesting experience, with both trains likely to be longer than the loop itself. The solution is well described in one of the M&GN books - can't remember which though. Basically, one train stopped short of the loop. The other brought a loops-length of train into the loop, leaving the rest of its train behind. Then, the first train drew through the loop, coupling up to the back of train two. The front half of train two then carried on forwards beyond the loop for some distance. Train one then brought the rear half of train two into the loop, uncoupled it and left it there. It then reversed back beyond the loop and forwards through the empty road in the loop and on with its journey. The front portion of train two then backed up to recouple with its rear half before carrying on with its journey - or something like that anyway.