You seem to recall the important parts - using a PVC boom and dowel spreaders.
What do you still need?
I've built several quads using W4RNL's dimensions here:http://www.cebik.com/content/a10/quad/2mq.htmlhttp://www.cebik.com/content/a10/trans/ant-design.html
There is also an online calculator using his equations somewhere, but I found an error
in one of the element spacing dimensions.
One was a 4-element design for 465 MHz using the same construction method that
I threw together quickly for some DF work, and it had a great pattern without any
length adjustments. Because I was in a hurry I soldered the loops into squares and
tied them to the sides of the spreaders with plastic strips. It would have helped if
I had secured the spreaders better to the boom, however, as they tend to slip around.