So I'm tried getting os_sapien to use some of cmt's tags and some of killers's reach marines but the problem is I get a error saying tag file is too large. Do I need something extra?

Do you get a debug logged?
Open your debug.txt file in the Halo Custom Edition directory and go to the very bottom segment.
Copy paste the paragraph you see to here.

11.23.15 22:03:46 tag reference name too large (this tag is corrupted).
11.23.15 22:03:46 failed to load shader_model tag 'masterz1336\shaders\marine_odst_set'
11.23.15 22:03:46 tag reference name too large (this tag is corrupted).
11.23.15 22:03:46 failed to load shader_model tag 'masterz1336\shaders\marine_odst_set_chest'
11.23.15 22:03:46 tag reference name too large (this tag is corrupted).
11.23.15 22:03:46 failed to load shader_model tag 'masterz1336\shaders\marine_odst_set_shoulders'
11.23.15 22:03:46 tag reference name too large (this tag is corrupted).
11.23.15 22:03:46 failed to load shader_model tag 'masterz1336\shaders\marine_attach_armor'
11.23.15 22:03:46 tag reference name too large (this tag is corrupted).
11.23.15 22:03:46 failed to load shader_model tag 'masterz1336\shaders\marine_badlands_set'
11.23.15 22:03:46 tag reference name too large (this tag is corrupted).
11.23.15 22:03:46 failed to load shader_model tag 'masterz1336\shaders\marine_spacemarine_set'
11.23.15 22:03:46 tag reference name too large (this tag is corrupted).
11.23.15 22:03:46 failed to load shader_model tag 'masterz1336\shaders\odst_helmet'
11.23.15 22:03:46 tag reference name too large (this tag is corrupted).
11.23.15 22:03:46 failed to load shader_model tag 'masterz1336\shaders\marine'
11.23.15 22:03:46 failed to load gbxmodel tag 'masterz1336\haloreach\marine\odst\odst'
11.23.15 22:03:46 failed to load biped tag 'masterz1336\haloreach\marine\odst\odst'
11.23.15 16:06:02 failed to load particle tag 'cmt\effects\particles\flash\impact flash'
11.23.15 16:06:02 failed to load effect tag 'cmt\effects\impacts\impact human armored'
11.23.15 16:06:02 tag reference name too large (this tag is corrupted).
11.23.15 16:06:02 failed to load particle tag 'cmt\effects\particles\flash\impact flash'
11.23.15 16:06:02 failed to load effect tag 'cmt\effects\impacts\impact human armored penetrate'
11.23.15 16:06:02 tag reference name too large (this tag is corrupted).
11.23.15 16:06:02 failed to load particle tag 'cmt\effects\particles\flash\impact flash'
11.23.15 16:06:02 failed to load effect tag 'cmt\effects\impacts\impact human armored'
11.23.15 16:06:02 tag reference name too large (this tag is corrupted).
11.23.15 16:06:02 failed to load particle tag 'cmt\effects\particles\flash\impact flash'
11.23.15 16:06:02 failed to load effect tag 'cmt\effects\impacts\impact human armored penetrate'
11.23.15 16:06:02 tag reference name too large (this tag is corrupted).
11.23.15 16:06:02 failed to load particle tag 'cmt\effects\particles\flash\impact flash'
11.23.15 16:06:02 failed to load effect tag 'cmt\effects\impacts\impact metal ballistic'
11.23.15 16:06:02 tag reference name too large (this tag is corrupted).
11.23.15 16:06:02 failed to load particle tag 'cmt\effects\particles\flash\impact flash'
11.23.15 16:06:02 failed to load effect tag 'cmt\effects\impacts\impact rubber'
11.23.15 16:06:02 tag reference name too large (this tag is corrupted).
11.23.15 16:06:02 failed to load particle tag 'cmt\effects\particles\flash\impact flash'
11.23.15 16:06:02 failed to load effect tag 'cmt\effects\impacts\impact metal ballistic'
11.23.15 16:06:02 failed to load projectile tag 'cmt\weapons\human\assault_rifle\bullet'
11.23.15 16:06:02 failed to load weapon tag 'cmt\weapons\human\assault_rifle\assault rifle cc'
11.23.15 16:07:11 MAXIMUM_RENDERED_OBJECTS exceeded.
11.23.15 16:10:48 there are no more free tag slots.
11.23.15 16:10:48 failed to load particle tag
Edited by ScarFOx on Nov 24, 2015 at 06:22 PM

I dunno much, but after a lil' bit of digging around apparently you need to use OS HEK to use these tags.
I'd recommend reinstalling OS 4.0 alongside OS HEK and retry with OS Sapien.

Did you showed your debug.txt of your Halo CE directory?. If you are using OS_Sapien to open the map, the errors are showed in other path (YOUR USER'S NAME\My Documents\My Games\Halo CE\OpenSauce\Reports\debug.txt). I need to see the errors located in that txt to help you.

I found out the some of the tags are corrupted so I'm using a different ODST and I'm changing the projectile tags on almost all of CMT's weapons

Do you want the Reach ODST Marine?. I can upload it to you. PM me if you want it
Edited by Isxz on Nov 25, 2015 at 10:23 AM

k