The two hands have a theme in common: Making a "normal" bid can be expensive if systemically with GIB it shows more total points than those held. That is nothing new, but it is still with us.
Hand 1
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Despite having 11 playing tricks I did not have the promised 29 total points for the 5C bid. 4C would have shown 25+ total points by the way.
What is meant by "Cheaper minor --", being the full description of the 3D bid? Yes it is the cheaper minor. By definition. The cheapest minor bid other than 3D would be 4C, which is more expensive than 3D, so yes, 3D is the "cheaper minor". 3C I believe to be forcing, so would it bid 3D on a Yarborough? if so, would a 4C follow-up by South be forcing on only 25 total points?
I suspect that 4C would have been the winning action. Possibly in part because North has enough to bid again anyway.
Hand 2
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Lacking the total points for 3C, 2C by South is the winning action, despite that it is non-forcing (I believe). Mind you, it is only JUST shy of the 19 TP required for 3C. Not that I would normally count 3 points for a kingleton. Mind you, if the Spade finesse had worked ... maybe not an unreasonable punt after all. Not one that I would have found.