> 	${X11BASE}/lib/X11/fonts/arphicttf/

To install them there for deleting directory completely after running pkg_delete
. (because of "mkttfdir")

> 	If there's any standard location, like for XFree86 4.x, pls let me know.

No, there are some description in "xfstt-1.1":

;1.1 How do I test it?
;
;        mkdir /usr/share/fonts/truetype and put some *ttf fonts there, now run
;
;        make xfstt && make install

some description in X-TT:

;2.4 Adding the Directory to the Fontpath (X Server standalone)
; --------------------------------------------------------------
;  Use xset fp+ or command line option.
;   
;  Example:
;   ========================================================================
;   % xset fp+ /usr/X11R6/lib/X11/fonts/ttf
;   % xset fp rehash

For nomal use, ${X11BASE}/lib/X11/fonts/TrueType is not bad,
it also be used as default path by "xfstt" package. :)