Practical? Eh-h-h-h-h. Useful for lowlight stages? Definitely. Will I make Grand Master with it? Well, heck no. In fact I am probably never going to get to Master anyway.
I got a O-Light Baton 3. IDPA rules say the distance from the bottom of the hammer slot to the bottom of the grip can't exceed 5". And yes HQ says a light mounted this way is to be included in the measurement. There are width and depth numbers but it is unclear how to measure them and the O-Light is so very close. This works well in dry fire, though my support hand is a little scrunched up, but MUCH better than a doing the rest-gun-hand-on-wrist-of-flashlight-hand, method. Plus this works strong or weak handed. Range testing Saturday then off to Belton, SC, IDPA Double Trouble with a night time match on the 18th.
NIT: I have an O-Light Baldr laser/light for picatinny mounting. Their magnetic charging cord is cool and easy to use. HOWEVER. The magnetic polarity of the Baldr is totally opposite of the Baton. As in, you can't use the charger for one on the other. I don't know if they did that on purpose because the charging is different but it's a bummer that the chargers can't be shared.