I prefer Rayon myself, as well.
As a newer vaper, I wouldn't have built such a low ohm coil initially (0.3 ohm). Sub-ohm vaping takes some getting used to. It took me two years to like sub-ohm coils. Even now, 0.6 ohm dual coils (two 1.2 ohm coils) is the lowest I build. Generally speaking, the lower the ohms the hotter the vape will be.
Also, 70 watts seems like a lot to me. I only vape around 30 watts. Although, with all of that metal mass with the Clapton coils, you probably need a lot of watts to fire them up. More metal mass requires more power (watts) and drains batteries faster.
You might consider building simple coils (either spaced or compressed, doesn't really matter) with kanthal wire to see what difference it makes. I'm a proponent of K.I.S.S. (Keep it simple, stupid). I've tried the fancy exotic builds before and although they can make more vapor, IMHO they don't improve the flavor. Ramp up time with simple coils is fast, and they don't drain your battery as fast as the exotic coils.