Bre reminded me of something I was going to say and forgot.
If he has never been in a shank bit before, maybe try these bits instead of the one you posted:
This first one is called a Sweet Six bit. You can buy the Sweet Six (Made by Sharon Camarillo) in a variety of mouthpieces (You can also find it in an off brand which is fine too). This picture is my favorite mouthpiece, also the same as the one you posted.
It's a soft bit, a little gag action, that is a good transition from the snaffle. The best part too is that there is a noseband you can buy to clip on or off of this bit as well. So if you buy it, try it without it first, and then if you feel like you may need the combo then put the noseband on. If you google "Sweet Six Bit" you will find a million results.
This next one is another favorite of mine, called an O-ring or just a Ring combo bit. I use it a lot to tune up my mare when she starts to tell me "f--- you" on the pattern.
I have the twisted mouthpiece with the dogbone, but you can find it in a couple different mouthpieces too.
The thing about this bit is that it's a great transition bit, super soft, but there is a lot of gag to it so there won't be as much "snatch" to it. Most of the "snatch" is going to come from the noseband, but the actual mouth pressure is very minimal.
Oh, another thing I didn't remember til now, you can also attach a noseband to a loose ring snaffle if you think that would be enough.