Wills have endowed the P Class with more than the usual number of location aids. Despite this, when I started assembling the locomotive body, I still managed to get the tanks slightly out of line with each other.
The great thing about whitemetal kits is you can usually put the bigger bits together dry to see if they fit. Then a little tack soldering will make sure you are right. Finally, the joints can be made properly with a seam if you feel the need.
From all this I concluded that it made sense to make the cab up as a sub-assembly. A couple of pegs were nipped off the bottom and the whole thing built up on my soldering slab.
One of the problems with this material is that on emerging from the mould it shrinks. Skilled modelmakers allow for this when making the master. Someone didn't do it right with the bunker back and I found if I wanted everything square then this was just under 1mm too narrow.
Not to worry. With everything else in place. a good fillet of low melt solder filled the gap. There's more work to do but it's all together. Even if I were gluing this kit together, I could have filled the gap but solder just makes life quicker, if a bit more "entertaining" when working with thin and meltable materials !