Vampire Synthesist

[OmnionMagnari]

Would a vampires str and dex bonuses work with a synthesist build?
how would the vampires hp work?
how would the natural armor work im doing the eidolon armor as armor and the vampire stuff as nat armor
how would saves work is fort based off con or cha?

[Lady-J]

the vampire stat increases are to you so the str and dex increases are only for you and not your edolon, the vampires hp is keyed off of cha(your edolons hp is still keyed off of con)instead of con, i suggest making your edolon be natural armor instead as that will allow you to use mage armor/bracers of armor plus the natural armor from the edolon will stack with the natural armor of the vampire, since your stuff keys off of cha now you would use your cha for fort saves