I’m waiting for three 16x-16x risers to arrive in few days, so I think the best option is to try one of those in that middle 16x slot to see if it works.
If it’ll not work I’ll try to short it…but I need to find a guide on how to do it properly in the 16x slot (that thread shows the pic of a 1x slot shorted), to avoid some nasty problems :P
Btw, thank you again for your help, I’ll let you know as soon as the 16x-16x risers will arrive!