I followed TwoXentrix's advice and ordered some 3/8" thick foam from Amazon - cut to fit into the recessed channels on the van top - length long enough (about 6 inches) to just catch the PH top at very front edge - and disappear under the PH to point it butts up against PH mounting edge - so when parked uphill or driving - the rain can't get under that foam and work its way into/under the PH front edge. Thanks to TwoXentrix - he's a wealth of SMB knowledge !
In my first several month associated with this Forum (and while I was looking to purchase a SM) I came across several accounts where members mentioned water leaks through the penthouse, so after I purchased my SM i took a good look at all the advise that was offered in those posts.
Quickly came to realize that the roof channels at the front of the pop-top had 'gaps' between the pop-top's gasket and the van roof - exactly where each channel was. I sealed this gap using 2 versions of soft Neoprene self-adhesive rubber.
(Links below from what I purchased)
FIRST: I cut the pieces to what I needed, then lowered the penthouse on top of the 6" wide neoprene foam rubber to draw the tops outline and identify where the tops rubber gasket actually met the roof.
SECOND: I used the 4x4 squares (first link) and cut them to fill the gap between the bottom of the channel & the top of the roof (1/2 neoprene accomplished this - but you need to cut the pieces so the outer edges follow the channel angle as it raises to the top - the ends need approximately a 45 degree angle outward).
THIRD: I cut the 6" wide soft neoprene sheet to the pop-tops outline: the front outer edge of the sheet is positioned about 1/2" in front of the pop-top gasket (allowing a little room since the pop-top moves forward & back a little), the 2 outer ends actually follow the curvature of the pop-top and extend back about 4" (that's why I used a 6" wide neoprene sheet). Even though the neoprene sheet was initially 6" wide, This 'gasket' is cut so it is about 2" wide along it's entire length (essentially it looks like a very wide "U" shape) - that's how it manages to follow the pop top edges (the corners) an additional 4" inches).
In step #1, I marked where the gasket pop-top gasket met the roof, this made it easy to first affixed the channel spacers, followed then by laying the 3/8" neoprene 'gaskets across the top of those - this keeps any water from being blown under while driving in rain, or drainage when van is stationary and the front elevated.
First set was in place from 2015 to 2023, just replaced them last year.
Before I put this on, I had noticed a lot of debris accumulate under the top, and now I have nothing...stays very clean & dry.
1/2" blocks I used for the channel filler:
https://www.amazon.com/gp/product/B09493P4L3/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
I was unable to find 3/8"x6" wide, so I purchased 12" and cut it in half:
https://www.amazon.com/gp/product/B089F2Y4MN/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
Pretty confident Pablo this would solve your issue. The other 'simple' solution would be to back your van in the same spot so front roofline slopes downhill.
