I have fitted the 14" round air cleaner. It has a deep (~1") recess in the underside. I put 3/8" thick expanded polystyrene blocks on the forward edge and the top nut to see if closing the bonnet left any indentations. I didn't see any, so I tried to film the inside of the bonnet when closed to see how much clearance there was. The video is here:
https://youtu.be/oX2-ctVTgs4 The film of the front edge is quite clear but the film trying to see the top nut didn't work as I couldn't get enough light on the place. Still, I am quite pleased with the fit. Now I need to go a drive to see if it's any quieter.
If I need more, the next step is to buy a used snorkel/silenced air cleaner and, if necessary, cut out its bottom and fit the recessed part of this 14" onto it.
David