Nothing wrong with single valve springs, but when I was looking at the engine I did recently, I noticed how hard it was to turn the engine over by hand. The valve gear requires a lot of force to overcome the springs. When I took them out, those springs were hard! Measured the seat pressure, and I don't remember the exact pressure, but 80 or 90 pounds comes to memory. The double spring ones are much less, say about 2/3 of that???
Forgive my memory. Senior moments and all. I just figured that the lower seat pressure was less stress on everything, which seemed like a good idea to me.
I got a guy here in Hamilton to measure stuff up, and press stuff apart etc. He was pretty good. Talk to Gus at the engine shop, in Norton rd here in Hamilton. I suspect you should not get him started on Ducatis. Pictures all over the walls..... We managed to get my crank pretty straight again. Within a thou all round. Make sure your end float is good. I may be paranoid, but I am going to check mine at each oil change. Point 45 mm after assembly for my 2005 450 FE.
Good luck, and let me know if you need any other info / help. The doc on the home page is priceless. Read it several times.