LESS IS MORE I

Change each letter group below into a common word by adding at least one letter to each side. The object is to add as few letters as possible. It can be done by adding 28 letters. That is, in four of the words, three letters have to be added. Those four words are given below as a hint. For the others, it's possible to make a word by adding only one letter on each side. S may not be used as the final letter.

1. _____HOV_____
2. _____NV_____
3. _____AIT_____
4. _____IFL_____
5. _____EHI_____
6. _____DEA_____
7. _____NS_____
8. _____LLE_____
9. _____HRU_____
10. _____ONO_____
11. _____TIO_____
12. _____LC_____

HINT:
#5, 7, 11, and 12 add three letters each.

Answers:

1. SHOVE
2. ENVY
3. FAITH
4. RIFLE
5. BEHIND
6. IDEAL
7. SENSE*
8. ALLEY
9. SHRUG
10. HONOR*
11. ACTION
12. MULCH 

*7. DENSE or MANSE 
*10. DONOR