I strongly suggest that you consider a two piece unit, i.e. a unit with the computer separated from the sensor screens such as Shooting Chrony's Beta Master chrono. There are two advantages to this, both important. First, you want the readout and controller to sit on the bench with you so you can see the display and operate it without having to walk downrange to the sensor. Second, if you accidentally hit your chrono sensor or the steel upright legs, you'll only damage the sensor and not the computer, hence your replacement cost for just the sensor is lower than a complete new chrono.
This Beta Master Shooting Chrony:
Not This Beta Shooting Chrony:
Get some plastic soda straws and black tape to mark 4" and 6" above the sensor. The plastic soda straws because they are both cheap and it struck, won't damage the sensor package if struck. You see, the steel rods are inserted into a plastic housing and if struck, they'll almost certainly break the housing. The tapes are reference points indicating the height above the sensors that the bullet should pass. Also, I'd recommend typing up a short list of functions on the top of the box so you can refer to it while shooting.
If you need to put the sky screen's up, I suggest that you take a second set of soda straws, fold a sheet of paper in two long ways, and tape your extension soda straw to the middle of each end. Then all you have to do is insert one straw into each of your marked legs and you've got a set that is super cheap to replace should you accidentally hit one.
The reason you want to do this is like flying a retractable wheel airplane, it's not a question of if your sensor get's hit somewhere, it's a question of when. Also, don't let your friends shoot through your chrony
, you do it for them. I made that mistake already. He only had to pay the $50 for another sensor unit rather than the cost of the entire unit.