Is Vanna relevant when Gamma scalping?

[Martinghoul]

Quote from TskTsk:[/i
What I'm looking for is basically a way to calculate P/L per scalp when you're long gamma and continuously hedging delta. As far as I understood, 0.5*gamma*S^2 is ~accurate, but I fear there are other factors at play that may influence my P/L per scalp, so my question is what would these other values be? I understand vanna is negligible...and I disregard any IV movement as I hold until expiry.

There's all sorts of other stuff... Why don't you experiment? Do your delta/gamma PNL explain and observe the residual. If the residual is too large for comfort, you've got a sensitivity to something else that needs accounting for. In my personal experience, you need exceedingly large positions to make the higher-order terms sufficiently significant to justify the effort.