Most pop tops are stored with the top up to prevent mould and dirt accumulating on the vinyl. I don't know what the manufacturers recommend. In one sense I would think the vinyl would be better preserved if it's shut in, but then again it would be easier to keep clean and dry open. Vinyl is my preferred annexe material, but after 4 years my awning roof has shrunk 6 inches both ways and gone brittle. It's also delaminating and falling to bits. Nothing is forever. What do the pop-top experts say?

We always store the  Hiace with the roof closed.   We had a camper trailer for 7 years in NZ and always had that closed when stored. All canvas in that.     Never noticed any problems with the Campermatic, nor with our present Hi Ace.     As long as the material is  dry and not damp when stored it should be ok. Of course the material is canvas, in  both vehicles.

We did have a VW Kombi years ago that had   "Pink and White" stripped (I know, I know)  vinyl  in the pop top.  Never any problem with that either. 

Having said that  I remember the vinyl was prone to condensation inside when up,   and us sleeping in it with not enough ventilation.

I would think that a little ventilation in  a stored vehicle would keep the air sweet as well.
Our  Hiace  has a weatherproof roof vent that is always open a little.   (fixed that way)  And of course the safety gas vent in the "Whizzbang"  door step   allows  air to flow.

I would suggest  the Tarp might not allow enough air flow through your van.  That is if all the vents are covered.   

Just a thought
Regards
Mike and Ellie   

We store ours down with a caravan cover over the entire van.  Even with Cairns wet weather we have had no mould or similar dramas.   I think that sunshine is the biggest enemy of vinyl as shown by  Granny's testimony.

 

When we first got our pop top I asked much the same question and have seen it asked many times since. On my initial question the consensus was to store with the top up. This would allow the springs on the scissor action to be relaxed and the gas struts to be fully extended and take the pressure off. I also hold the top up with some adjustable struts on the corners of the pop top to take the weight off from the awning. Also use these when set up on a CP. On the other hand other answers have been the opposite. It all depends on what you believe to be correct for you and your van.

all the best,

Terry.

I just got a new van........I asked the same question..was told with new modern materials.......its not a problem having roof top down........as long as its dry...incase the struts start rusting.