Great stuff, although you can't blame me if you don't like it
Yeah the guy line mod for the door looks like a good one, I just switched the guy the one time I've needed to move the door but his method is less fiddly, especially if it's cold or poring down.
Seems like an age ago now, pretty sure the first time I sealed it I didn't thin it down, just got a small brush and daubed it on whilst pitched. I have resealed around the top and mitten hooks fairly recently though and that time I thinned it down, definitely made it easier to work with and get a neater result. Plus some say thinning it down allows it to soak in to the threads a little better meaning it's more efficient at proofing the seam so it's worth thinning it down a little I reckon.
If you can do it on a dry day so you can pitch it and apply the sealant whilst it's pitched, again I think this might help it get in to the seams and threads a little better, but then what do I know
Make sure you let us know when it arrives and how you get on with it
Matt