I've made quite a few ocean spray bows, and they all get taken down to the pith (or past). The problem with ocean spray is that it checks like crazy. If you leave the bow thick (not down to the pith), it's going to want to check down to the pith anyway to relieve the stress created during drying. I wrap the handles in painter's tape for a few months to keep the handle from checking, and some still do anyway. On some historic pictures of native bows (gull-wing designs) the pith is visible on the back of the bow, so they definitively reversed them at times without a problem. I think the next ocean spray bow I make will be reversed - I was even thinking it might be nifty to cable back the bow and use the pith as the guide. It's not exactly as efficient as a raised cable (TBB!) but could look cool.