without wishing to undermine anything chris has said:
i use running tension when doing 2v cam timing as the first one i did years ago was with V2 cams and that's how they told me to do it. so it's just my convention. overtightening the belts retards the timing, ime about 2 degrees from the running tension setting. certainly on a 4v motor the difference between 3 and 11.5 on the gauge is 1.5 - 2 degrees. i don't have the adaptor kit for the tool to suit 2v motors, but similarly the difference between running and "tight" i've found is about 2 degrees. so my setting of 106 say i'd expect would be 108 overtight.
given i'm sitting in the office having lunch i've just had a look in a few 2v manuals - 900m 95, 99 and 01. the 95 book has a reference to offset keys if required, but no mention of how to check. the 99 and 01 books say to tighten belts to 11.5 on the tool (overtight) and check the timing that way then adj as required, 99 with offset keys, 01 with the std adj pullies.
but with std comp you can usually advance a long way and not get pinging issues at all. my 600m at the std 115 inlet c/l was fine, but 107 inlet c/l was rough at lower revs - the 600 has 11:1 comp std so that's why.
as chris says, i'd retard the cams until it stops pinging. i'd actually do it to see what it does to the top end - it'd be the first place i looked for my missing power. actually, it'd be the second - i'd do runs with lessened ignition advance first, but then i have stuff to do that and you don't so it's not something you can do. unless you can get the ecu reflashed with less ignition advance, which is a better idea in theory, but not so in practice maybe. cam timing is just a setting that you make based on lots of other stuff, and more comp has a clear effect on what you can or should run.
as an example of applications and bad ones thereof - years ago we did a 900ss for a customer with some minor porting and v2 210 torque cams. had a real nice midrange, but fell off quickly. we then sold it to someone else who wanted a 944 kit as part of the deal. the reports below show it all, and what can go wrong when you have high comp and midrange based cam timing.
BikeBoy.org - 900SS CARB WITH SOME VEE TWO CAMS
BikeBoy.org - 900SS CARB WITH 944 KIT
this graph shows my std comp 750 with big vavles and 900 cams, green is 107 inlet c/l, red 119. big difference, 119 not better anywhere
http://www.bikeboy.org/graphs/750mg8.gif
this graph shows my high comp 750 motor - green is 113, red 107. as you can see, the 113 has a top end advantge, more so possibly in the shape of the torque curve than actual number, but the shape is the important part.
http://www.bikeboy.org/graphs/750mg16.gif
that's why we are saying retard them. we don't know for sure it'll change the shape of power curve, but it's a logical step for the two issues you have. and because no one has built that engine before that we know of, no one knows for sure. it's all suck it and see at this level (then tell us about it so we know too).
think i'd better get back to work.