To answer two separate questions :- The correct ‘deep’ cylinder head retaining nuts are half an inch deep, so have plenty of grip onto the studs.
Tom Ward’s guide rods are very simple to make, and you need two of them. As they carry no load they can be made out of mild steel rod, 3/8″ diameter, and 5.5″ long (minimum). Put about one inch of 26TPI cycle thread on one end, and a screwdriver slot on the other end. To use them, screw them into two of the cylinder retaining bolt holes, one on each side, just finger tight. These help the barrel to be lowered smoothly and ‘square on’ to the crankcase, and when the barrel is ‘home’ just remove them, using a screwdriver if necessary, and replace them with the retaining bolts and spacers.
Mine actually are Tom Ward’s, and they were given to me many years ago by the late John Hartshorne, at a time when he was without a Scott for a few years in the 1980’s. John was Tom’s business ‘sleeping partner’, and company secretary at Ward Motors Limited.
I also have Tom’s old notebooks, which are full of interesting information.