scotch wrote: ... The in-tank screen would prevent damage to the valve-cone and body from any foreign material scratching the surfaces...
Yes, this is exacly why I'd like to get a screen put back in.
scotch wrote: ...
I can only presume that your OEM valve leaks! This can sometimes be fixed if the scratches aren't to deep in either the nylon valve-cone or tapered bore.
No leaks yet. I initially took the tap apart to clean it because it wouldn't' move. I managed to clean out the crud and free the tap without any damage but it's a poor design as crud from the tank continues to collect in the valve cone/bore and make it inoperable (it's already stuck again). A better design - even with the screen in place - would have included a small sediment bowl - like most taps - under the valve cone. At this point, I don't want to risk moving it - as it'll scratch the tap bore as you suggest.
PS: thanks for eyeballing the screw spacing.