Removing tenacious screws: use a heaty-up screwdriver device or soldering iron (make a screwdriver end for it?); insert in screw-slot and wait until it turns. Make sure that the screwdriver that you turn it with fits precisely.
Removing old glue: hot water and rags. Heat gun: this is extremely effective, but how to protect shellac surfaces against the heat? They bubble rather quickly.
Grain direction – check in all planes possible.
Glueing the splat – cramping worked on the top split, but failed on the bottom one. Re-glued with wedges (managing to scuff one of back legs: cave protect surfaces).
Splat should remain loose top and bottom.
Don’t use ratchet stretcher to cramp chair together; use sash cramps, to avoid movement in vertical plane and to ensure even pressure.
Colour-matching stretchers – Vandyke crystals worked beautifully on one, but other piece didn’t take so well. What to do? Applied garnet polish but still not dark enough.
With thanks to Cliff Deighton