dash vent tubes

[mcosh]

My dash vents and the tubes they slide into have become loose and rattle. I was going to drop the dash out enough to get a sealant gun in behind to silicone the aluminum tube at the back.

I see on the RV8 pages its suggested I remove the dash steering cowling. As I only want to drop it forward enough to get behind has anyone done this before? Would appreciate any advice.