First off I don't think there is any such thing as sexual compatibility. Compatibility in general is a must, and if both people are generous and enjoy giving as well as receiving in all aspect of life sex will be fine. Only if one or both are shallow and have prejudice will sexual compatibility be affected, and you will want to know a sexual partners floors before having any type of sex regardless whether or not it's within marriage.
That being said, I don't think there is anything wrong with pre marital sex as long as both consenting adults know where they stand and what type of relationship they are in. All precautions should be taken to avoid unwanted STI's and unwanted pregnancy.
Just remember consenting to sex is like consenting to drink tea, sometimes if an adult consents to sex they may change their mind or be incapable of sex moments later. So if they can't drink tea, they can't consent to sex.
https://www.youtube.com/watch?v=OBTxIQAg1aw
Kate xx