[timgr]

I mostly lurk here, but I might have some useful suggestions for you.

It was mentioned above, but I would point out that both the DB8e and Y10713 are large antennas, and you will need lots of room in your attic to hold them, and even more room to aim them the direction that you want. If this is a stick-built building, the attic will be full of collar ties and struts that stiffen the roof and support the ceiling below. Since attics are not built for human habitation, there is not a lot of unimpeded open space, typically.

If the building was built with trusses, there will be even more struts in the way.

Before you sign off with your landlord, get your tape and start measuring the unimpeded space in the attic. IIRC the Y10713 has a 10 foot beam (the main beam is 10' long, and the other antenna elements sprout from that) and the DB8e is a 4'x4' panel. You could make a stick and cardboard mockup, take it in to your attic, and see if there is any way to position it optimally.

You could also grab a portable TV and extension cord, and move it around in your attic, to get an idea of the degree of shielding you must contend with. Measure everything you can. I'd also start with one of the two antennas (the DB8e) and see how your attic works out before committing to the very bulky Y10713. If the attic shields out UHF, I would bet that it shields out VHF at least as effectively.