Once the snugness issue is dealt with you can deal with forehead fit. Invariably you will notice an area of redness on a part of your forehead after wearing a new full-face helmet for several minutes. You can cure that with the use of a large spoon.
Use the backside of that spoon and compress the Styrofoam in the part of the helmet causing the marks. You will not have to remove the helmet liner to do this.
After you assure that the cheeks and forehead are fit properly you need to assure that your ears are not contacted in any way while wearing the helmet. Whether you have had earphones installed or not it is imperative that your ears are free from contact.
To cure any problems you will have to pull away the liner and use a knife and cut away part of the Styrofoam around the ear wells within the helmet. A little too much is FAR preferable than not enough!
(After an hour of wearing a helmet that binds your ears in any way you will be in simply awful pain)
2) You can soak the skull cap in water before putting it on & it will keep you nice and cool on very hot day