Is there such a thing as too much Tongue Weight?

No. The only exception is if being above 15% causes the payload rating of the TV to be exceeded. Should never ever be below 10% when you are all loaded up for camping and ready to head off. Tongue weights around 10% are typical if you look at factory dry weights, but any published dry weight is useless info. for determining TV and WDH ratings and limits.

Here is a 2014 thread that discusses the topic of being over 15% TW. Downside to tongue weight over 15%?