Oil ratio and shocks

I’m doing my own mix for my P200E (1981!) as it doesn’t have an oil tank. I used to use Silkolene when i was back in the UK, and was quite happy with it. Now, I bought the Sip fully synth, and a bottle of Malossi 7 as a treat for its new cylinder. Ok, it may be overdoing it as the machine has a stock engine - and a Sito exhaust - and I ride quite slowly.
What do you recommend for the ratio of the mix? Silkolene clearly stated 2% on the bottle, neither the Sip nor Malossi state a ratio. I went for 2%, but the exhaust fumes are a bit embarassing (which could also be down to the engine being old and oil leaking from the gearbox into the engine).
My big overhaul also included changing the shocks for a pair of Sebac. What setting do you usually use for the rear? I started with the lowest position, but rapidly realised that the Vespa was riding without springs and there was about one inch before hitting the bottom.
Thanks, Pierre