Post Alabasta episodes were individual episodes and were decent.
Goat Island was three episodes and sucked.
Rainbow Mist was four episodes and sucked.
Apis was seven episodes and sucked.
G8 was 11 episodes and rocked.
IceHunters was nine episodes and rocked slightly less.
Maybe there's a peak of episode length before quality starts coming back.
So 11 episodes of goat-fucker would have rocked?
I think the quality of fillers is more determined by:
1. Does it fit into the anime or does it interrupt it?
2. Who is in the center of the filler? Strawhats or filler kids?
3. Is the comedy up to Odas standards or not?
4. Does it screw the rule of Odaverse or not?
Apis: 1. Hell no 2. Kiddo 3. No way 4. Yes
→ Damn it!
Goatfucker: 1. fits 2. Filler gramp 3. Nope 4. No
→ Kinda bad
Rainbow Mist: 1. fits 2. whole bunch of 'em 3. No 4. time travel and different dimensions?
→ Next to worst
Foxy Round 2: 1. i was happy it is over and than it started again 2. Strawhats 3. Yes 4. No, or yes? Two Zoros?
G8: 1. fits, 2. Sh, 3. Up to, 4. No
Oceans dream: 1. No (W7 belongs directly after Aokiji) 2. Sh 3. Not really 4. A bit
Icehunter: 1. fits 2. 50-50 (fights without them) 3. No 4. No
Spa Island: 1.fits 2.kids. 3. comedy? 4. no
→ So-So again
Ps: OpenOffice spelling proposal for Odaverse: Oversexed