There is no correlation that I've ever seen between Retrieval stats or scores and the rarity of items obtained. Combined with what I posted above about the drop rates of Iron Voyage Spoils, I feel that the best ship for farming the Iron Voyage Spoils is one with the highest speed and lowest Retrieval. Surveillance isn't bad either, which increases the chance of getting two items. Sure, you could aim for Optimal scores, which give you a chance at getting 2 at once, but wouldn't you rather have a ship that can do two trips in the time it takes the other ship to do one? More trips means more chances of getting the drop you want. But, there's no real reason to hit any other sectors if all you want are the mounts, so you don't need much hull. So, I'd go with one of these two ships for farming spoils:
The Monster Hunter - Maximum Speed, high Survey, low Hull, minimum Retrieval
This ship is designed specifically for hitting SC24 as often as possible, maximizing the chance of getting Iron Voyage Spoils (ie: Zu Mounts). Drop rates for these items are 1-2 for Optimal yields, and 1 for all other yields, so getting a "disappointing" yield is only slightly worse than an "optimal" yield. This makes the Retrieval stat nearly useless for obtaining them. Hitting just SC24 should take about 26 hours and 23 minutes. This version of the ship has a little more Range, allowing it to also hit one other sector from this list if desired: SC01 (adds 1h35), SC02 (adds 1h58), SC05 (adds 2h43), SC06 (adds 2h57), SC07 (adds 3h12), SC08 (adds 4h12), SC09 (adds 4h05).
- Hull: Invincible
- Rigging: Viltgance
- Forecastle: Odyssey
- Aftcastle: Bronco
- Survey: 126
- Retrieve: 46
- Speed: 154
- Range: 60
- Favor: 122
The Monster Trainer - Near maximum Speed, high Survey, low Retrieval, minimum Hull
This ship is designed specifically for hitting SC24 as often as possible, maximizing the chance of getting Iron Voyage Spoils (ie: Zu Mounts). Drop rates for these items are 1-2 for Optimal yields, and 1 for all other yields, so getting a "disappointing" yield is only slightly worse than an "optimal" yield. This makes the Retrieval stat nearly useless for obtaining them. Hitting just SC24 should take about 26 hours and 46 minutes. This version of the ship has a little more Retrieval, allowing it to obtain more items on average when you fail to get Iron Voyage Spoils. It also has very slightly less Speed and Surveillance.
- Hull: Bronco
- Rigging: Viltgance
- Forecastle: Odyssey
- Aftcastle: Invincible
- Survey: 122
- Retrieve: 60
- Speed: 150
- Range: 46
- Favor: 126
These have been added to the third post.
Hopefully sometime soon, we'll get a bit more Rank, allowing for a Tatanora or Viltgance piece to be used alongside another Viltgance piece. Right now, using a single Viltgance limits all other pieces to Odyssey or lower.