Oh, and try this exercise..
R L R R L L R R R L L L R R R R L L L L
ie: Two singles, two doubles, two triples and two 4 strokes.
First learn to play it.
Next put an accent at the start of each hand in each bit.
R L R r L l R r r L l l R r r r L l l l
Then when you want a challenge..
Put the accent on the LAST stroke of each section.
R L r R l L r r R l l L r r r R l l l L
By the time you work this out in matched grip your left hand will have the muscle memory it needs.
Then, play songs with your left hand on the hats and right on the snare. Like Simon Phillips. This will give your left hand the strength it needs..
I am currently teaching my 11 year old to play. Baby steps. It easier for him to take instruction from a stranger drum teacher than me. Despite that I have him playing open handed. He is now playing the hats with his left hand, but ride cymbal with the right. I wish I was taught that way when I was 5 (when I started playing).