Installing number boards on older Kato N Scale locomotives

[Big Train]

This in my Covid-19 lock down project right now.

Need advice for installing the separately applied number boards on the cab and trailing end. I've never done this before and was wondering what recommendations anyone may have to ensure they stay in place. I think Kato designed these as a friction fit but I have seen locomotives where these have disappeared. Knowing these are custom made for each locomotive, getting replacements would be impossible.

A drop of ACC seems like a logical idea. I know from some of my other modelling activities, PVC or white glue cam also be used. Are there other solutions?

Any advice is appreciated.

Stay safe

[RBrodzinsky]

I  use a drop of Allene's Clear Gel tacky glue

[NorsemanJack]

I install the number boards, clean inside the shell with a swab with alcolol and then apply Microscale Kristal Klear across the back of them (i.e. inside the shell).  I don't want to risk getting any adhesive on the surface of the number board or around the opening on the exterior of the locomotive.  I have routinely done this to all Kato F units, due to the "press fit" that doesn't always hold.  I've never lost one, but have found them in the jewel cases from time to time.  Not anymore!  IIRC, their E units and PA units use a more robust mounting.

[u18b]

I agree with all of the above.

An extra danger of superglue is that the vapors themselves can cause a kind of frosting effect.  For example, if you put a micro drop of glue at the base of a window glass.   Then the next day, some frosted appearance might be on your window.

And besides.... the other suggestions are not permanent.   You may change your mind one day.  ACC is a bit more permanent.