I actually prefer the barbed fittings (for exactly the reasons you describe, plus it is easier to inspect for duff connections), so there is no problems there. However, do you know if the barbs are designed for a particular diameter tubing? I don;t think the 3mm tubing I was planning to use is going to stretch over the barbs without something breaking, and even 4mm tubing is looking a little tight...

Cheers
Andy