For as inexpensive as they are.... Just buy one...
I have a Shooting Chrony Beta model... Have had it forever. Never an issue (unless you leave it on and then the 9 volt goes dead and you never have a spare in the house)...
I am happily married with a really bad fishing obsession and a developing archery obsession. I told my wife that archery will not be nearly as expensive as Great Lakes fishing. I need to slowly acclimate her to archery. Somewhat like cooking a lobster I guess. I am still not allowed to have a father's day, birthday or Christmas present this year due to my autopilot upgrades for my boat this year. The archery shop in town has a prochrono digital that I have been thinking about acquiring, but also read about making one which would be interesting to mess around with also.
To answer your question earlier Lab Rat, I think I am still going to tune on the Z for a bit before getting into the Cat. I need to sit down and document what I have done and the results in a tabulated fashion. Since I have it probably shooting as fast as it is going to with major gains per change I really need to put together a DOE plan for anything further I do. That way I can quantify results and understand what is responsible for what.
Once I have that all done in some fashion and am satisfied that the Z is tuned as well as I can get it for the capabilities of my equipment I will move onto the Cat.