Vbit feeds and speeds are weird, there is basically no great universal formula or at least I was not able to crowdsource one from the collective brain on this forum, the best guideline that emerged at the time is what I captured in that section of the shapeoko ebook, and it has served me well:
In addition, here are two examples of (successful) vcarve jobs in hardwood and richlite (similar hardness) with one of my 25° vbits, you might want to dial down those settings slightly for a 15° vbit
Experimentation is key. To minimize the risk of breaking the tool, start with very conservative depth per pass, rather than slowing down the feedrate. The tip of a vbit spins at essentially zero RPM already, so moving too slow would rub the wood rather than cutting it. Depth per pass on the other hand is the perfect tuning parameter to go easy on the tool (slow depth per pass = very little deflection/ lateral force on the tool). Then incrementally increase depth per pass so that the vcarve jobs don’t take ages to complete.