Yeah, someone insisted on putting a bit like that in Bear's mouth, he HATED it. He did best in the normal snaffle (w/ no shanks), then he did second best in the tom-thumb.The short shank snaffle IS A CURB BIT. Many times the curb bits with a snaffle mouthpiece (like the one you are referring to) are more harsh than a curb bit that has a port.
When you transition to a curb bit, look for these kind of curb bits: correction, spoon, or reiner. Look for something with swivel shanks and a mouthpiece that has action (not a solid mouthpiece with no movement).
A curb bit is not harsh if you select the right one & learn how to use it properly.
I hate you for posting that link, now I think I've found ANOTHER Christmas present for Java... The Calvary Shank at the bottom looks like it might work well with my heavy reins for finesse work. But that California Shank wouldn't be bad for a new daily bit... hmmm.