Height and weight written out

In formal writing I like to do this (in British style):

• The infant weighed 10lb 5oz;
  a 10lb 5oz infant

• He was 6ft 3in tall;
  a 6ft 3in man

My question is about the plural usage: do we have to change

The infant weighed 10lb 5oz.

to

The infant weighed 10lbs 5ozs.

Or not?

I say no, but I’m really just reaching out for confirmation here.

Also, would you use my examples — with abbreviations for pounds, ounces, feet, and inches — in formal writing?

If not, how would you write it?

If he is 6′3″ tall, then he’s a 6′3″ man, or a man who stands six foot three. We don’t say he stands “six ∗feet three”, but rather “six foot three”. Notice we don’t actually spell out inches there, at least not normally, because it’s completely obvious. So we just drop it. Usually.

Sometimes, though, you do make both plural because it would sound weird to have inches but foot rather than feet, so if you say inches in the plural, go ahead and say feet in the plural: “He stands six feet, three inches tall.”

Assuming he’s human, that you could say that he’s a real six-footer, he is, since only insects are six-feeters (well, six-footed, but still), not men — no matter how much they bug you.

And while you might have a ten-pound baby, you would say that the baby weight ten pounds. You do not make the unit plural when using it as a prefix; see?

This is all covered here.