Jim : Excellent suggestions! And I would wholeheartedly agree - especially on the development data set.

I am guessing the exceptions would have been 2021-22 Bear and possibly the Stagflationary period - I think ( guessing here without having the data series in front)
towards the end of it - when Volcker started to raise signficantly ie the 1980 and 82 mini recessions. But IIRC - Gold and Silver ( some massive cornering by some TX folks - IIRC I read from an article) rallied like crazy then.

Both of these are out of my data set - since you have THE model - I am sure you know the explanatory drivers and mine come in 2 windows. All that go back to 90s and EVERYTHING going back to 2003.

I will try and test these and see if they improve IN-SAMPLE and HOLDOUT fits. We can always have 2 versions running.

Always appreciate your thoughts and invaluable insights! You were the inspiration for my efforts

Best
AC