I'm no foamy, but I think you should keep in mind that a limerick is essentially a joke. If there's not a firm punchline in your mind, it's probably not going to work well as a limerick or pseudolimerick.
There once was a man from Lahore
Whose limericks stopt on line four.
When asked why that was,
He responded, "because."
I don't remember where I heard that one, but it illustrates the underlying principles of this genre of poetry pretty well. It's funny because you're expecting a fifth line in which the poem will be resolved with a clever, rhyming punch line. Even if you can't come up with an actual
joke, you should at least give your limerick a firmly-defined
point.
There once was a poet called Durabys,
Who stared quite too long at the abyss.
The abyss, it gazed back
and called the poet a hack
for his poems it found to be piss.
Cut me a
little slack on that one -- I wrote it quickly to illustrate a couple of points. Consider the meter, for one thing
I don't know a lot about meter, but I know that rhyming lines should flow similarly. In the above example, it's not perfect, but the syllable counts are all very close, and the stress patterns are similar. Compare the breakdown I just did with this one:
There's three main problems, here -- first, the inconsistency between rhyming lines makes it really hard for me to tell what to stress and what to leave unstressed to preserve a pattern. Second, the inconsistency itself is a bad thing -- it destroys the cohesiveness of the poem. Finally, there doesn't seem to be much of a point to the poem itself. A good limerick concludes with some shift in the audience's perception. For instance, the one I just composed (which I don't claim is good) goes from "There's a poet" to "he's gazing into the abyss, thinking dark thoughts" to "the abyss is gazing back" to "the abyss thinks his poems are dumb." There's a juxtaposition there that surprises the audience, throws off their expectations, and injects a bit of humor.