The Firmness/Comfort Levels when comparing your latex matresses.

Hi, i'm a 5 foot 11'' man, slim, and weigh around 12 kilos. I have a good matress already it's a hypnos, all natural, hand made springs. Problem is I think it's slightly too hard for me, I turn a lot trying to sleep on my side and wake up sometimes and I believe this is because the matress is slightly too firm for me, so i'm considering getting one of your natural latex toppers. First, may I ask why does your guide suggest that the fusion 3 full matress would be softer than the fusion 4, since both use the same density topper; what i'm asking is; does the slightly higher density of the fusion 4 base actually result in a noticeable difference in firmness? Also, do you use dunlop latex on your matress bases and the more expensive latex on your toppers? Any information you have will really help me out. I look forward to hearing your reply. Peace ?