Epic v10 sport volume

Is because of weight (70kg) that this epic v10 sport keeps tipping me out? i also have an Ozean 00S4 and its the same beam of 48cm and it is far more stable. The epic is padded at the hips. its a blue tip. it is just so twitchy ive tried ballast too! 

Sorry to say you are on the wrong ski for your ability. The V10 Sport is still a racing ski for intermediate paddlers, not beginners. Nothing to do with your weight. I paddled a V10 Sport for many years and was averaging just under 15km/hr downwind, that is quite fast, compared to most intermediate paddlers who are around 12-14 km/hr.

You need to be on something like a V8. You will have much more fun and you will learn to paddle much faster as opposed to learning to swim and re-mount!

Beam width is the most important variable in determining the stability of a ski, but it is not the only one. I once paddled a SLS10 (spec ski by Epic) and to me it was terribly unstable, although I was very used to the V10 Sport at the time. Both boats have a maximum beam of 48 cm.
The blue tip is the heavier version of the Epic skis, the boat weight should contribute to increasing stability a little bit.
Cockpit fit is also a factor. Many people say that the V10 Sport has a wide bucket. If you have very narrow hips you could sit very loose in the ski and that might make you unstable. Maybe the fit in your OSS4 is tighter?

Is it tipping you out in rough water, or even in flat water?