I have one -- just got it recently from Fountain Pen Domain (penseller.com -- photo of
Stipula Bellini from penseller's site). The pen itself is smaller and lighter than Stipula's usual offering of pens (excluding those Stipula compact, pocket-sizepens). It is 5.5" long (capped) and I'm not sure on the barrel diameter, but it's quite slim for a Stipula.
If you've handled a Stipula I Castoni College, they are nearly similar in length and barrel diameter, but the Bellini's cap is heavier. The rose gold trim is quite nice and will add weight if you post your pens -- but the balance may be a bit off because the pen itself is quite light (which suits me). I haven't inked the Bellini yet though because I'm still trying to work through my current pens in rotation. I may give it a go tomorrow.