I can't hit the mag release on any of my pistols without changing my grip, and that is the way I have been doing it forever.
Recently it has occurred to me that I should probably be using the thumb on my left hand to hit the release and maintain my grip
and sight picture while snagging a full mag and inserting it. Duh
For those that can't reach the release with strong hand w/o changing grip how do you go about it?
I am right handed and none of my pistols have an ambi release. Would it be better to install ambi releases and press them with trigger finger from right side of the gun?

I use my trigger finger to release both mag and slide, lefty here, on my HK's.

My other hand left/right, is used to pull a full mag, never to use the mag release.

Are we supposed to guess what kind of handguns you have???

You could try installing an extended mag release.

Most people either do that, or just change their grip when reloading.

If you wanted you could change the mag release over and use your trigger finger like lefties do.

Another lefty here and I use my trigger finger. Much easier than using a thumb. If you have the option of a reversible mag release, put it over on the right side of the pistol so you can take advantage of what we lefties have been doing since mag releases were designed.

Some of the top shooters in the world can't reach the mag release without shifting their grip.  Watch Rob Leatham shoot a 1911 or Ben Stoeger with his old Beretta or new Tanfoglio both shift their grips.  This allows their support hand go for the next magazine right away which will be faster.  I do know a couple of people that press the mag release with their support hand, one who recently started doing it is Athena Lee who is a competitive shooter and she seems to like it but she also has extremely small hands.

The way I see it if it works for you and it is fast and efficient then run with it, but you don't see any of the top level competitive shooters using that technique and they are at the very top of pistol shooting performance.  

I have the same problem as does most every shooter I know of. The "right" technique is the shift grip, but I do as you describe- my thinking in a high stress situation is the last thing you want is to shift your grip get fumble fingered and drop the gun. My support thumb is moving past the release on the way to the spare mag anyway. I figure for me maintaining a solid grip and my mag change being a millisecond or two slower is better. Without shifting the grip it is more likely my grip will be right after the reload and therefore my subsequent rounds on target.

Another lefty here.  Use my trigger finger for mag release.  Been doing it to long to switch over now !

I am a southpaw and frankly even a "ambidextrous" mag release doesn't work for me on ANY gun. Over the years, I have just developed a unique method of performing magazine changes. It isn't what any professional would teach you to do but it works for me. It isn't perfect but I practice to keep it smooth and efficient which gives the illusion of being fast and seamless.

I have large hands so reaching the mag release on any pistol has never been an issue.  For you find a way that works best and train yourself to use it that way.  Honestly their is no wrong way to do it .... You might hear the tier one guys say do not adjust grip or yada yada yada whatever but at the end of the day none of use are built mechanically the same.  My neighbor who I shot with has elven hands so he has no choice but to adjust grip.

Keep shooting and use what works well or try different techniques till you find what works best.  Maybe even get a friend to run a timer on you and do some drills while trying different ways to do a reload.  The timer will tell you which is faster.

My hands are not large so I shift my grip when I dump a mag. Most fast competition guys I know do the same thing.

Here is another thought for you... if you can reach the mag release without shifting your grip, are you going to hit the mag release during recoil when your grip is not perfect? I have a tendency to hit the slide release during recoil on my M&P. Since I find this very bothersome and have to make an effort to ensure it does not happen, I would rather have to shift my grip ever so slightly to drop a mag.

Go to carry for past six yrs is a M&P 9c
Also have and carry about the property and occasionally into the real world:
M&P 9 fs
M&P 45 fs
And newest is springfield TRP , no holster yet but when I do get one this will be a possibility as well.

Guess if changing grip isn't a bad thing then I will just continue trying to smooth it up.
Thanks for the help