If it were easy to do a little dihedral would help on THIS setup
The rub is - the strength of the wing root is compromised
As for stability - really not an issue.
OnTHIS setup
The big change is that the relationship of th vertical area including the fin n rudder - is changed quite a bit

The application of rudder will cause roll in the opposite direction and simply turning with a banked wing (not always re'q'd) -WILL be a little different
Go ahead and do it - . See what you can learn
PS- some of my extremely aerobatic stuff has dihedral
CAPS/EXTRAS/ZLINS-all have dihedral and setup right, are very neutral .