Walberg - I'm probably opening another can of worms here, but I wouldn't dry mount to any kind of foam board. I have seen the board collapse, or compress in areas, which can be seen viewing the print. I've also seen foam core do this in sections, if the heat in the dry mounting process is too high (or long, or pressure too much).
Why do you mount to foam board, anyway, just curious?
To each their own regarding dry mounting, but I always refer back to the photography conservationist I had a conversation with. Her name is Patty Landres, and works/workes at the Minneapolis Institute of Arts. When I first started seriously photographing, and asked her advice for mounting my prints, she very assertively exclaimed the following: "Whatever you do, do NOT dry mount your photographs. Ever".
And then began to explain to me what a pain in the neck it is to try to save a print where something had happened to the board the print was mounted to. You may draw your own conclusions, but I don't think advice gets more expert than that.
Advances in Archival Mounting and Storage by Michael A. Smith and ‘Inherent Vice’ and Quality A Photograph Conservator’s View by Barbara E. Lemmen) played a big role in my decision. I get the ArtCare Archival Foamboard through a local framing shop. Controlling the entire process from taking the shot to mounting the print is a hobby for me. My prints are not destined for a museum or for profit. They are destined for my pleasure and the pleasure of friends and family and the occasional art gallery supporter who is willing to support the gallery by buying one of my prints. I donate a print, and the gallery sells it in an auction as a fundraiser. It's my way of donating to the gallery.
As for your concerns, they are valid, and I have taken measures to avoid such problems. Besides using archival foamboard, I have refurbished my drymount press so the temperature is quite accurate and the pressure is minimal and uniform. I have never had the foamboard fail.
It's your print, you are the artist, sign it any darn place you want any way that works.
I sign mine with fine point Sharpie on the lower right, with a title on the lower left, just in the white space outside the picture area. If someone thinks that gouche, well, tough noogies.
Thats what I was taught by my photography professor. Do not do anything that can not be undone. Never dry mount ,and sign with a pencil rather then a pen, referring to fiber based prints. For RC prints I would think a pen would be ok because it is coated and not likely to bleed. Signing and titling the print on the bottom white border was acceptable, but it really a matter of personal preference. If you photograph is strong enough signing it isn't distracting. I would worry more about un spotted dust spots or someones hair getting trapped between the print and the glass, now that is distracting.
Linen hinges. That or supply your mounter with reversible mounting sheets; almost all "professional" framers have only the permanent kind. I sign on the front with an extra fine Sharpie and have yet to see any bleed or creep. (I may come to regret using that.) I also sign in very soft pencil in the middle of the print's back. No problems there either.