The builder of my loco chose to use 4BA steel hexagonal socket cap head screws to attach the steam dome to its bush, similarly, the regulator assembly uses the same fixings.

I am removing these screws as there is a weep from the regulator assembly. Removal is proving difficult enough where there is space aplenty, i.e. the steam dome but the dome is now off and I shall probably use alum to eat away at the remnants of the screws. I have yet to tackle the six screws holding the regulator assembly in place.

What is the current thinking for replacement screws. I have it in mind to use M4 x 20mm marine grade stainless steel hexagonal socket cap head screws or even M5 if space permits.

Is my thinking flawed?

The builder of my Tug deviated from Don Young's plans in many ways. Pencilled in on the drawing of the regulator are the words, 'Use Bullock regulator valve'. I haven't been able to find any information about this variant. Can anyone help?