1. Start MC 2.5.x or 2.6.x or any version PRIOR to 2.7X!!!!!!!
2. Edit the script of card 1 of stack "home"
3. Add these lines to the script:

on preOpenStack
put "MetaCard" && the version && the platform && "engine"\
& cr & "Copyright © 2001 MetaCard Corporation" \
& cr & "All Rights Reserved" into field "Copyright"
repeat for each line l in the customKeys["preferences"] of this stack
if the number of words in l is 1
then do "set the" && l && "to the preferences[" & quote & l & quote & "] of
this stack"
end repeat

######## The following lines!!
if the version >= "2.7" then
start using stack "mctools.mc"
if the platform <> "MacOS" then
open stack "mctools.mc"
end if
set the defaultStack to "home"
reset cursors
end if
########
...

4. Close the script, save the stack and
5. you are ready to use MC 2.7.x, after updating the engine inside the app
package
as described in an earlier post.