installing valve seals

[gestalt1]

while installing the valve seals i noticed some of them were fairly difficult to press on. i used a socket to press them and they would not budge, i then taped the socket with a hammer and they seemed to still not budge. they are on fairly good but not all the way seated on the guide. is this normal? should i worry about them coming off the guide? these are the brown/black seals. thanks, matt