In the Feudal Scots list, the notes state "Upgraded yeoman can form 1/3 of any Yeoman TuG and be deployed as a front rank", and TUGs must eb 6, 8 or 9 bases, So how does this work for a TUG of 8. If deployed 3 bases deep, and 3 bases wide - then upgrading the front ranks this is not 1/3rd. Similarly if deployed 4 bases deep, and 2 bases wide - upgrading only 2 bases is also not 1/3rd. Pedantic ? yes but someone somewhere will claim it is not legal. Easily rectified by changing to "upto 1/3" but is this the intent? Easier in the later lists which specify "any" may be upgraded.
So upgrading Yeoman is only valid for TuGs of 6 and 9. Live with it.
Richard