Unfortunately your combined weight exceeds that to which we test our mattresses. We test our beds using a 200kg roller (31.5 stones). The weight is rolled across the mattress 20,000 times to assess general durability of the mattress. However, this weight is always moving on the mattress and not left stationary. Therefore, the lifespan of your mattress is likely to be reduced.
With regard to the different levels of comfort you prefer we would suggest you consider the zip and link option offered by The Pocket Spring Bed Company