They're always a cause of trouble, aren't they?
In this case it's the lining on Conway Castle which is causing the headaches.
This diesel emerged from the works at the start of the 1990's with a rather intricate tri-tone livery to match the new push-pull carriage set - intricate for a narrow gauge diesel, that is - and Himself has been trying something clever to get the ultimate definition between the colours.
He has been making his own transfers by cutting very thin slivers of waterslide transfer paper and then painting them with both the shades of green used on the model.
Then he's applied them give a perfect break line either side of the cream band around the middle before adding on the straw lining.
The problem is that the lines are too thick.
(I suspect I wasn't too popular when I told him that after he asked my opinon.)
The first time he was using a 0.5mm wide straw line but there is a 0.35mm available so he's going to take a little break, give his tired eyes a rest, strip it all off and try again.