Weight difference

Hi, I weigh 13 stone @ 5ft 6 & my husband 20 stone is 6ft 7. We have tried 3 Emma mattresses & about to return the third & ask for a refund as a ridge forms in the middle & a dip on my husbands side.
Could you recommend a mattress please? He is a side/back sleeper & I am a side/front sleeper. Thankyou
Tina