In short, Farley of MBARI took measurements of the mast and estimated the thickness of the metals with JimScholfield.  Farleys assessment was that it was good for loads to 800-1000 lbs.  The rigging and hoist were selected to accommodate 500 lb loads.  Rigging was to be rated to 1000 lb (5:1 built in) and line to 4000 lb.  In reality everything exceeds these ratings.  
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Short email communications from the boom rating process (old to new):

Hi Farley,

Jim and I shot the aluminium structure on the Paragon.

Our best guess for readings - Forward diagonal braces 1/8 inch thickness.
                                          - Main vertical mast 1/4 inch 
                                          -Boom 3/16 inch 

Note the readings had some variability due to the curved surface.

Chris 
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Ok ,  Thanks Farley.

Hi Jared,

If we assume our current max load is 400 lbs and double it for acceleration  we are at 800 lbs . Running rigging should be 5 times our load so 4000 lbs or 2 ton hardware. 

Jared can you review the the hardware on the Paragon and bring it up to a 2 ton minimum rating . So the turning blocks, winch, shackles, and lift wire  need to be 2 ton or greater SWL.
No Chinese stuff and preferably stamped with a load  rating. 

Let me know if you have any questions.

Thanks,

Chris
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Hi Jared,

Upon further review I would like to modify my previous  email for Paragon ratings.

If we use a 500 lbs limit that Jared proposed we need a minimum rating of 1.75 times ( 46cfr189.35 wet weight handling gear uses 1.5  ) so 875 lbs pounds is what the structure should be rated for.

This falls  within  Farleys  rating of 800- 1000lbs SWL for the boom/mast structure .

At 875 lbs the wire or rope should be a minimum safety factor of  5 , so 4375 lbs. Since turning blocks have moving components they should be
  considered running rigging so a 2 ton rating would be appropriate.

Chris 
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Ok, Sounds fine . I think we have wiggle room on the safety factor for the blocks. I can't find anything definitive on whether these should be considered running
 rigging so I left in the the 5:1 safety. If you have issues with sizing for 2 tons we can revisit.

Also, something to consider when specifying  a sheave. The line is typically supported by the sides and bottom of the sheave so it doe not flatten out when under tension . Your small plasma
 line is flatten over the existing wide sheaves and does not appear to have this type of support.Not sure if we can address this with the new sheave selection.

Cheers,
Chris 
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On final conclusion, hoist and rigging equipment have 5:1 safety built into them, so we targeted 1000lb SWL on rigging and 4000 lb on line.  

In reality, we are well above on everything, but the hoist is a 1000 lb rated unit.  If it were a winch it would be about a 4000 lb winch.  Twice the strength of the one it is replacing.

Jared's notes.