How to write limericks

I'm finding some satisfaction at my work. System design problems to solve - number crunching, algorithms, a smattering of statistics and signal processing. Now I remember why I'm employed.
The patent committee have started prodding me on some work I did a year or so ago. I lost interest, figuring it would never get resourced. I procrastinated on detailed diagrams and figures. Now it looks like I have to extract the digit.

I borrowed a book about limericks from the library (because of a little idea I'm working on but more of that later). I hadn't realised there was such a strong expectation of innuendo in the limerick. Well, I'd better try my hand:

On a poetic soap-box I climb
for a limerick isn't just rhyme.
It has rhythm in threes
which should come if you squeeze,
but to add dirty meanings takes time.

It is right to write three anapests
as a limerick's line form suggests.
Then there's two lines with two
where the topic turns blue
so the last line can finish with breasts.

Our discussion of rhythm and beat
in this art form would not be complete
if we didn't give tips
on the use of one's lips
to embrace its full passion and heat.

A very strict form of the limerick finishes the last line exactly as for the first, but with a different meaning. This is, of course fairly restrictive. (The usual example quoted is "Nantucket" vs "Nan took it".) Here is my attempt at the strict form:

I can't ever ask you to pity me
not even if I live to ninety three.
Your face, it's a nun's
when faced with my puns.
Of patience it is the epitome.