Can one use alternate evaluation methods, e.g. "K&R" to defend actions that appear to violate your convention card?
This issue was discussed on the Bridge Laws Mailing List a few months ago:

Do players have to describe what they play?

Cribbing from my own post there:


  Edgar Kaplan (the "K" in K &amp; R) wrote to the effect that the
  convention card is an understanding with partner, not an undertaking
  to the opponents.
  
  HCP are an approximation of a hand's value. The laws do not mention
  them. Absent regulation to the contrary players must be allowed to
  evaluate their hands using their own judgement, promoting and demoting
  as they deem best. Some such regulations have been passed. While I
  consider them harmful to the spirit of the game they are lawful.


For what it's worth I use K&amp;R evaluation at the table, as do some of my partners, but I don't do it on every deal. It is time consuming, so I use it only when I'm not confident how to evaluate the hand. I do not indicate this on my convention card, and I'm not sure how I would. It's a complex method that cannot be explained in a short paragraph.

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Update Jan 1, 2016

I think I let myself get sidetracked, missing the heart of the issue. The K&amp;R evaluation method is merely an example. Tom does not use it at the table, nor I suspect is he likely to. More to the point, there is nothing magical about K&amp;R. It was intended to reproduce the judgement of one particular expert, Edgar Kaplan. For instance he devalued a hand if it was 4333, as do most experts, so the algorithm does the same. Likewise for stray queens and a host of other factors.

The real point is that Tom, or any of us, can evaluate a hand as we please. If I list a range of "15-17" for 1NT on my convention card it does not mean that my partner, my opponents, or anyone can count on me to hold exactly that many points. Rather it's a shorthand for saying that I will open hands that I evaluate to be in that range. I might well hold an excellent 14 or an ugly 18. For me neither happen often enough that I would write "14+ to 18-" -- that would only be misleading. My partner plays me for 15-17 and he and my opponents are equally well informed.

Those who've read Victor Mollo will remember the Walrus, who blindly follows the point count no matter where it leads. Nothing in the rules or regulations of the game requires us to do likewise.