Unlike in previous games, Serious Sam 4 has various skeletons that you can use to give your player model a different height compared to Serious Sam's, whom is the tallest one available. The smallest is Nonna and the middle most height is Aubrey. You can load these skeletons or base your player model off their player models for the sake of your sanity.

All these skeletons can be exported to .fbx and used in blender by going to the Skeleton Editor and exporting .fbx from the right side menu.

Serious Sam 4 introduces proper third person melee and driving for player models as well as custom first person hands. These need to be declared in your models .nfo in order to work.

Custom First Person hands are .mdl's based on the arms in Models/Weapons/Arms/Arms.mdl. Create your own version of these arms and save them somewhere, be it in your model folder or in the weapons/arms folder. Make sure to save the .bmf as well, SED does not like local meshes. Once you have created your Arms_CHARACTER.mdl, go to your .nfo and input the following line:

FIRST_PERSON_ARMS_MODEL="Content/SeriousSam4/Models/Weapons/Arms/Arms_CHARACTER.mdl"

Then test if your arms appear, they will load in the editor or in the moddable client.

To enable your model to be seen in first person when driving vehicles or meleeing enemies, you will need to do 3 things.

Declare Third Person Avatar in your .nfo by adding this line:
FIRSTPERSONAVATAR="YES"

Hide your avatars head and any sections that block your view:
Go to your layer maps for your models head, hair, hats or what ever may be in view. If your model for whatever reason is made of one or two layer maps then manually split it for your own sanities sake so that the area above and around the shoulders is on a seperate layer map.

Inside the layer map scroll down to Rendering Conditions and do the same as I have below. This will cause the sections you designated in that layer map to temporarily disappear whilst driving or meleeing enemies:


Adjust Skeleton ViewMover if location isn't ideal:
If, after removing parts of the layer map, your camera is not in an ideal position then you must resave your player models skeleton. Then go to the Skeleton Editor and move the bone named "ViewMover" either up, down or whatever direction you have to in order to get the camera angle you want then save the skeleton.

If your character is smaller than normal or has oddly shaped arms or hands, you may find that they do not grasp the handlebars or steering wheels of vehicles correctly. Using the IK of the vehicles, this can easily be adjusted in the Model Editor.

Go to your character model and in the bottom right corner of the view port is a dropdown box. You will find these two options:

RightHand_IK_EndEffector
LeftHand_IK_EndEffector

Adjust these by moving them in the view port. The location of these 2 holders will dictate where your hand is placed for the IK system.

NOTE This will have an effect on the way your model holds weaponry.

Note:
Remember that 'TTRS:PlayerModel.MasterChief.Name" - The MasterChief section is your models identification tag. Try to make sure your tag does not match any other player models tag on the workshop or in Serious Sam 4 or it will cause errors and may make things like descriptions not work correctly.

The Description is your models little quote below their frame.