Using the newest update, I have a dweller in training for Luck with a Level of 59. He has a Bangor (- 29% Training (continuous)) as a pet with him......... The other pets for Stim and Rads speed up are useless. The experience and wasteland return speed enhancements are good.

The above dweller (Austin Allen) is now at level 65 and in Luck training with the Bangor cat. I thought that Level 50 was the highest Health possible? After more training I will send him out to see his time in the wasteland. Unfortunately he did not get the "level 1 endurance buildup".

Woah, that's odd. Maybe it's a glitch? None of my level 50 dwellers will go beyond 50. Oh well, thats actually a good thing for you then!

What happens if you assign the cat to someone else, does the first dweller show as only a level 50, or is this a permanent change? You could really have a big advantage in HP by swapping that cat around every few days.