Scull Length?

[caaitlin]

I am a school girl rower- 65kg, 175cm.

I recently moved clubs and so all my gear is not set for me yet so I've been mixing and matching until I have time to set everything.
The other morning I put my oars on the ramp and found I'd grabbed two different lengths so I figured I better actually put a tape on them and find a pair the same length. I had the choice between 287.5, 88 inboard or 285, 87 inboard as I didn't have a screwdriver on me and was in a rush. I decided on the 287.5 pair as it was flat water and we were doing low rating pieces (so I thought!)
At my old club I used a pair which were 286, 88 inboard however I am more of a 'thumper' than a 'rater' so I wonder if I would actually be best to keep the long oars instead of changing them, or even only know a tiny bit off them.
I havent done winter training and as I head into racing season I am struggling in my getting fitness back (my fault.)
What is everyones opinion on what I should do regarding oar length?