OK. Here's what I've found. I have one recipe, from Catalan chef Josep Lladanosa i Giro, but it offers nothing on the curing and drying, so it is of little use. Actually, from all of the general information I've found various places, plus the information in the PGI application, I think I can give you enough to formulate your own, or at least research some of the other information, such as the humidity and drying regimen for the Parma region (I'll get to that).
Salchichon de Vic / Llonganissa de Vic is a medieval sausage, and it uses a common (and near perfect) ratio of salt to pepper of 4:1 or 5:1 that has been used in Catalan and Italian sausages since at least the early Middle Ages. When I make fresh butifarra for a crowd, using this ratio, I get raves and people want to know what all is in it. They never believe it when I tell them it's just salt and pepper.
This sausage is very simple: minced lean pork, diced fatty (streaky) bacon, salt and pepper, dried and cured for at least 45 days, with a fine patina of white mold on the surface. So, the ingredients must be outstanding. Modern descriptions mention garlic, nutmeg, coriander, and cinnamon, but the traditional recipe is simply salt and pepper, and that is what is protected under the PGI. This sausage is known for its red color of perfectly cured pork, and visible pieces of black pepper when it is cut. The ingredients are allowed to sit for 48 hours, covered and refrigerated, before stuffing. It is stuffed into 35-90mm hog or beef casing, 20-90cm in length. Average diameter is 70-80mm and average length is 50-60cm.
The basic formula (percentage of meat block) is:
lean pork (ham, loin, shoulder, trimmed of fat) 80-85%,
bacon (always referred to as bacon, not pork bellie) 15-20%,
salt 1.7-2.1%,
course-ground black pepper 0.4%.
Total fat content should be around 15%, so I assume 95% lean pork, and 80% fat bacon. Your guess is as good as mine as to whether this is calling for (cured, unsmoked) bacon, or fresh pork bellie.
I have no information on temperatures, humidity, or target weight loss. What I have learned is that the Plain of Vic has a very similar climate to the Parma region and the Po Valley in Emilia-Romagna. So, think dry, but with fogs from the plain, mist from the surrounding mountains, and humidity from the ocean, as in Emilia-Romagna. I'd rely on the expertise of others, here, who have worked with dry-cured sausages to help you relate this sausage to others from similar climate conditions as far as drying and curing go.
If I were going to attempt a recipe, I'd start with, per kg of meat:
800-850 grams lean pork pork shoulder, minced (medium to very fine grind, as preferred)
150-200 grams very fatty side bacon, diced medium to very fine
4 grams freshly-ground coarse black pepper
If using UK Cure #2:
13.6-17.6 grams salt
2.65 grams UK Cure #2 (or 2.5 grams US Cure #2)
If using US Cure #2:
13.8-17.8 grams salt
2.4 grams US Cure #2
I have no idea what to tell you for innoculation and curing. Others with more experience will have to help you with that. The mold you want to achieve is similar to a Fuet. Here is a good picture:
Salchichon de Vic
Here is the PGI application describing the protected Salchichon de Vic:
http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:C:2001:096:0008:0010:EN:PDF
I know this isn't a lot to go on, and coming from someone who hasn't actually made a dry-cured sausage, yet, but I hope it helps. Hopefully, others who have more experience will come along and correct any mistakes I may have made. Good luck!