Thank you, Ryan. The link you posted is essentially th same as the one posted in the thread I was referring to....I had thought I'd made it easy enough to find the thread from last December.
With the spec sheet in hand, I was able to allay the fears of those who had been taught "no holes," etc. I really don't know how the job could have been completed had I been confined to the "knock-outs."
As a general practice, I did try to place my holes closer to the middle of the web, but I also had many long pulls, and the ductwork usually filled the space, forcing me to work near the edges.
The spec sheet says "an 1 1/2" hole may be made anywhere in the web." I took full advantage of this, as my holes were 7/8".
These joists have webs made of a material similar to particle board, and most seemed to be about 3/4" thick, though some had webs as thick as 1 1/2". The 'flanges' are of pine lumber, approximating a 2x4 with a milled slot for the web. They are manufactured to order, and are made in any length you want. The lumber part is spliced with glued finger-joints, and the webs appear to be butt-glued with a hot-melt glue. Joints are, of course, staggered.
