Okay, well here would be the exact process you should take:
1. Open itemdata.txt
2. Find your 7D armor
3. Copy the appropriate armor code over the BSR path for each piece.
Code:
item\china\man_item\heavy_07_ha_super.bsr
item\china\man_item\heavy_07_sa_super.bsr
item\china\man_item\heavy_07_ba_super.bsr
item\china\man_item\heavy_07_la_super.bsr
item\china\man_item\heavy_07_aa_super.bsr
item\china\man_item\heavy_07_fa_super.bsr
(for girls, you should use "\woman_item\")
4. For adding extra space, I suggest you search for "worldcup". You will find the World Cup event items which are a pretty safe bet because I doubt they would ever reuse them for another event. Look for
Code:
0 xxx item\etc\drop_ch_eventbox.bsr item\etc\e060607_worldcup_g.ddj xxx
and replace it with
Code:
0 xxx xxx xxx xxx
(Note that for adding extra space you do not need to copy shorter resource names over the old ones like it sounds like you did. All you have to do is type an xxx over the old path and it will nullify it.)
5. Now save the file as "itemdata.mod" and open it up in your hex editor.
6. Right click -> Properties on itemdata.txt (the old file) and look at its file size in bytes. Now in your hex editor, look at how many bytes itemdata.mod is. With HexEdit it should be in the lower right of the frame. Subtract the file size in bytes of itemdata.mod from the file size in bytes of itemdata.txt to get how many bytes of null padding you need. Put your cursor at the end of the file and go Edit -> Fill. Then type in the number of bytes of null padding you need and hit okay. Finally save the file and inject it back in to Media.pk2.
This whole guide assumes you are of course working with an up to date itemdata.txt file. Re-extract it just to be sure.