Sika-flex is an awesome sealant! I have used it to seal a sidewalk to aluminum storefront in Manhattan. The sidewalk had plastic expansion joints and it had a basement below it. The Sika-flex keeps the water out. Good move on trying it, I don't think the pine needles will hurt the job...
I forgot to mention - No leaks!!! looks like Sika sealed it. We have had a lot of rain, including a few heavy downpours. Not a drop in the floor pans since I did that. I think I finally got it.:thumbsup: