Spined or Spinned (Spin) [duplicate]
Solution 1:
Spin > Spinned*
Spine > Spined*
If the syllable in one-syllable words have the structure of (C)CVC, the last consonant is doubled when suffixes are added, eg. stopped, tipped etc.
EDIT This is only theoretical as an answer to your n/nn question since 'spin' is irregular (with 'spun' as its preterite/participle) and 'spined' is, I believe, an adjective found only in combinations like 'broken-spined'