The combination of 90 kg and a C121 will work very nicely. And it was (as per 2005), as I recall, just some 67 cm wide which means that it can candle at least a 6.0 very nicely. The same should be true for the reintroduced 2010 model of C121.
Get a used board in the 120 liter range, like the C121. You will be able to uphaul it, with some concentration (not as easy as with 160/79), and you will have loads of fun with the 7.0 and smaller.