Hi All I have made a list of collision mode numbers inside fpe files and what the numbers mean. Just open a fpe file and scoll down until you see collisionmode = "number"
If its a character you will see ischaracter = 1
for more details see list below:

Collision modes and shape type:
11 = No collision
50 = Tree collision
10 = Hull Decomp
1 = Polygon
0 = Box
9 = Convex Hull
12 = Empty nothing in collision shape
3 = Cylinder
22 = Animal that follows the terrain landscape
2 = Sphere
No models as of yet use collision mesh
ischaracter = 1 means it’s a character

I hope you will find this useful

THK
Soundstudios

Docs/CollisionModeValues.txt : (GG Classic but are still same values in MAX AFAIK)

// collisionmode:
// 0 ; box shape (default)
// 1 ; polygon shape
// 2 ; sphere shape
// 3 ; cylinder shape
// 9 ; convex hull reduction shape
// 11 ; no physics
// 12 ; no physics but can still be detected with IntersectAll command
// 21 ; player repel feature (for characters and other beasts/zombies)
// 40 ; collision boxes (defined in Import Model feature)
// 41-49 ; reserved (collision polylist, sphere list, cylinder list)
// 50 ; generate obstacle and cylinder from 1/64th up from base of model
// 51 ; generate obstacle and cylinder from 1/32th down from base of model
// 52 ; generate obstacle and cylinder from 8/16th up from base of model
// 53 ; generate obstacle and cylinder from 7/16th up from base of model
// 54 ; generate obstacle and cylinder from 6/16th up from base of model
// 55 ; generate obstacle and cylinder from 5/16th up from base of model
// 56 ; generate obstacle and cylinder from 4/16th up from base of model
// 57 ; generate obstacle and cylinder from 3/16th up from base of model
// 58 ; generate obstacle and cylinder from 2/16th up from base of model
// 59 ; generate obstacle and cylinder from 1/16th up from base of model
// 1000-2000 ; only one limb has collision Box Shape (1000=limb zero,1001=limb one,etc)
// 2000-3000 ; only one limb has collision Polygons Shape (2000=limb zero,2001=limb one,etc)

Thank you both for the information!

// 0 ; box shape (default)
// 1 ; polygon shape
// 2 ; sphere shape
// 3 ; cylinder shape
// 8 ; polygon shape using OBJ file
// 9 ; convex hull reduction shape
// 10 ; hull decomposition - multiple convex hulls
// 11 ; no physics
// 12 ; no physics but can still be detected with IntersectAll command
// 21 ; player repel feature (for characters and other beasts/zombies)
// 22 ; no repel (for animals that player can pass through)

The one you want for using a separate OBJ file for the collision mesh is collisionmode=8.

// 40 ; collision boxes (defined in Import Model feature)
// 41-49 ; reserved (collision polylist, sphere list, cylinder list)
// 50 ; generate obstacle and cylinder from 1/64th up from base of model
// 51 ; generate obstacle and cylinder from 1/32th down from base of model
// 52 ; generate obstacle and cylinder from 8/16th up from base of model
// 53 ; generate obstacle and cylinder from 7/16th up from base of model
// 54 ; generate obstacle and cylinder from 6/16th up from base of model
// 55 ; generate obstacle and cylinder from 5/16th up from base of model
// 56 ; generate obstacle and cylinder from 4/16th up from base of model
// 57 ; generate obstacle and cylinder from 3/16th up from base of model
// 58 ; generate obstacle and cylinder from 2/16th up from base of model
// 59 ; generate obstacle and cylinder from 1/16th up from base of model
// 1000-2000 ; only one limb has collision Box Shape (1000=limb zero,1001=limb one,etc)
// 2000-3000 ; only one limb has collision Polygons Shape (2000=limb zero,2001=limb one,etc)