A few comments and suggestions on this theme for Howland.

Summon I: Definitely stronger than most summons of this level. It has twice the HP though. This is maybe a bit much? Perhaps reduce its total HP by 1/6th.

Summon II: All around, stronger than most summons of this level. Seems well balanced though considering I often prefer to use a level 2 buff than this spell. Although, this is the only summon in the theme that has two attacks a round. It also has a higher AB than the next two summons.

Summon III: Definitely requires Weapon Finesse. This summon's AB is only +1 because it has such a low Strength score. Weapon Finesse would make it comparable in power and usefulness to the other summons; although even then its AB is 2 less than Summon II. So far, its been easier to kill than the level one summons, probably because it only has 4 more HP than the Summon I. Its AC is 5 lower than Summon I or II.

Summon IV: The AB on this is 2 lower than the AB on Summon II, and its AC is 3 Lower. I would consider raising its Dexterity score by as much as 6 to 8 points.