How it feels
Firm. Not medium-firm with a marketing asterisk — 7 on our compression gauge, and our 175 lb tester found it uncomfortable by night three. This is a specialist mattress built for a specific job and it makes no effort to be anything else.
Under our 240 lb tester, the same surface felt like a well-judged medium-firm. That is the whole point: firmness is a function of the load on it, and the Plus is calibrated for a load most mattresses never see.
Support
9.8, the highest number we have recorded. The comfort layer is latex rather than polyurethane foam, which does not develop the compression set that causes heavier sleepers to flatten a mattress within two or three years, and the coil unit beneath it is a heavier gauge with a reinforced perimeter.
Spinal alignment held inside two degrees of neutral for our heaviest tester on his back, which no other mattress in our records has managed at that weight.
Edge support
9.8, effectively tied with support for the best figure in the review. Our ten-minute seated test produced 0.7 inches of compression at one minute and 0.75 at ten. There is no creep and no roll-off, and for anyone who sits on the side of the bed to dress that is not a small consideration.
Durability
The reason to buy this rather than the standard Luxury Firm. Latex does not take a permanent impression the way foam does, and Priya's density measurements on the base foam came back at 2.1 lb/ft³ against a category norm nearer 1.8.
Three-year centre sag on our unit is 0.2 inches under a heavy sleeper, which is the same figure the Saatva Latex Hybrid recorded under a lighter one. In this weight range that is remarkable.
What you give up
Pressure relief, at 7.6, is the weakest score of anything we recommend. Side sleeping on the Plus is uncomfortable at any weight under about 250 lb and merely tolerable above it. If you sleep on your side and you are heavy, this is a genuine conflict and there is no mattress in our test set that resolves it well.
Motion transfer at 7.2 is the worst in the review. Firm latex over firm coils transmits everything.
Who this is actually for
Sleepers over about 300 lb, or couples with a combined weight over 500 lb, or anyone who has flattened the centre of two or more mattresses inside five years. Within that group it is the only mattress on this site we recommend without reservation.
Everyone else should buy the standard Luxury Firm and save $250.
The full context is in the the best mattresses for heavier sleepers guide, which explains why foam density is the number that actually predicts whether a mattress will survive you.