Good to hear. It sounds like you have the key on a separate key chain from your Yukon keys. Otherwise, as pointed out above, you would not have access to the lock with the vehicle running. I guess it would be prudent for anyone considering a key lock mechanism to call Lock'er Down Safes and speak with the owner about your specific vehicle and situation. I'm not sure what real advantage if any, a key mechanism provides....My 21 Yukon lid will close with the key in my vault.
As for the four-digit tumbler lock, all members in my family know the combination and what number needs to be changed to quickly open it. Easy peasy and no extra keys to lose or fumble with. To each their own.....