Here is my feedback as a HTC Vive Player.
Don't assume the grip on a Vive Wand works the same way it does in Oculus Touch.
HTC Vive grips are very hard to press and can be painful to hold. So, you wouldn't want the player to keep holding the grips to hold an object unlike in Touch controllers. Since the player would need to exert a lot of force and is going to have pain in the finger.
On Vive if you want to hold an object and release it as soon as the player releases the input, you'd want to use the trigger. You use grip only when togglling drop or pickup. Using it to hold an object as long as the grips are pressed should never be used since the grip is too hard to be kept being pressed for a long time.
I assume you don't know about the fault in Vive Wand grips since you don't own one. But most games use the above mentioned method in Vive instead of the one you're using. Infact Recroom doesn't use grips for holding at all. It only uses it for rotating. It uses trigger for holding and pickingup and the menu button for dropping.
I would recommend using grip for toggling picking up and dropping and for objects that need be held as long as the input is held like those physics blocks use trigger. I guess you'd need to implement pickup and hold and drop systems. Where pickup keeps holding the object as long as drop is not pressed, drop drops a held item and hold holds it as long as the trigger is pressed. This I guess should only apply to the Vive wands and not other systems since Oculus Touch it is very comfortable to hold using the grip.