Question about Keymaps

[R H]

I apologise for posting here--I rather suspect this is not the
appropriate list.  However I haven't any clue where my question would
be more appropriate... and this question on generic linux forums goes
unanswered, save for a myriad suggestions of unpleasant work-arounds.

I would like to be able to customise the behavior of my dead
keys--either under US International keymap or under a different/new
one.

Specifically, I would like the following things to happen:

^ + o = ő (<- o with double acute accent on top)
^ + u = ű (<- u with double acute accent on top)
' + p = p' (<- *2 characters*, 'p' + composite acute accent [visually
one character--though physically two])

and other things as such.

I do not want to produce various characters by alt+### key
combinations, or via shifting the entire keyboard via an xmodmap mode
change.  I want to use *dead keys* specifically.

I even found the likely suspect file for achieving this... namely
Compose files.  One of mine is the file:

/usr/X11R6/lib/X11/locale/en_US.UTF-8/Compose

It contains information on what key combinations (including dead keys)
should produce what characters.  However my changes seem to have no
impat *at all*.  (well, I did not try deleting the files--but sensible
edits certainly do not appear to result in any change)

How can I customise my dead keys?  If it is through the Compose
files--which one should I be editing?  If it is not through Compose
what?

If this is the wrong forum, please direct me to a more appropriate
place where someone might know the answer... this has been making me
crazy!

Thank you in advance!

Roland