475 LB 340gr Loads.

So I got my bullets and I'm ready to load. My plan was to load 4227, but it turns out that I'm out of it. All I have on hand is WW296. I saw JT's article where he loaded 350 grain bullets in the 475LB from 29-33 grains of WW296. I'm thinking with the 340s I could start maybe 29.5 grains loaded to the longest advertised length and crimped hard with WLP primers.

Does that sound like a safe start?

I'm a little apprehensive with 296/H110 with new loads.