Plenum fasteners

I'm getting closer to fitting this RV Bits plenum. Note, it didn't fit very well for the price. Thankfully fiberglass is pretty easy to modify or I would have made one. Gel coat is fracturing off too so I'll have to get jiggy with the sander and grind it all off.
It will be time for fasteners soon. I can't find any best practices regarding fastener spacing. A few photos on builder web pages look to be about 3" apart.
Anyone with a plenum care to share the spacing please?

I sent some photos to your email address, Larry,- pls let me know if you don't get them. I actually made a test box and pressurized it with air to test spacing of various configurations. 3" seemed be a maximum. The only place that had a long row was on the aft baffle. You will see where they are, and how many - mainly placed a screws in certain locations and filled in-between. Few ended up 3" apart, mostly 2.5".

Here is a pic

I have had good results with this spacing. Can't see it, but I laminated an annulus in the intake ducting to continue the fastner spacing across the plenum lid-intake interface as well.

Piano hinge wherever possible. Essentially zero spacing and self sealing. Also lightning fast to remove/install.

Photos

BillL said:

I sent some photos to your email address, Larry,- pls let me know if you don't get them. I actually made a test box and pressurized it with air to test spacing of various configurations. 3" seemed be a maximum. The only place that had a long row was on the aft baffle. You will see where they are, and how many - mainly placed a screws in certain locations and filled in-between. Few ended up 3" apart, mostly 2.5".

Click to expand...

Yes, excellent photos. I also replied. Yours is very similar to mine so I was hoping for more photos of the inlet area. Thans everyone for the photos and details. Much appreciated