Tab 400 Fantastic Fan Vent Cover install

@Giota, use the search box at the top of the screen.  Enter a word or two that address what you are looking for.  I entered the word "roof" and found the discussion thread that @qhumberd is referring to:

https://tab-rv.vanillacommunity.com/discussion/comment/143310#Comment_143310

I searched "access to roof" and found these discussion threads:

https://tab-rv.vanillacommunity.com/discussion/9506/questions-on-installing-vent-fan-cover

 https://tab-rv.vanillacommunity.com/discussion/comment/83068#Comment_83068

I just installed an Aero-flo cover over the center vent.  I used a 12' step ladder beside the trailer.  I did not have to go on or over the roof.  I dropped the fan housing inside so that I could reach through to the roof after unscrewing the fan blade.

From atop the step ladder I drilled for the two near-side backets.  From the inside I drilled the two holes for the other side opposite the first holes.  I attached the 4 brackets from the inside.  I installed the cover's base from atop the step ladder...I could not see the carriage bolts on the far side brackets but I could feel for them to attach the washer, lock washer and nut set.  It worked quite well and I'm pleased with the result.  My arms are long (36-37" sleeve) so normally sized folks may need to lean over the trailer more.