The issue is/are:

(1) I want to have a rode that is over 200 feet long --200' (or 150' at least) of chain, plus rope (probably 150-200').

(2) The replacement chain/rope gypsy I can get accepts only 10mm chain (slightly larger than 3/8"). I currently have 200' of 5/16" chain.

(3) 3/8" chain weighs about 50% more than 5/16" --so, in order not to have excessive weight in the bow, and not carry 200 feet of 10mm chain (an equal length to the 5/16"), it seems like I could only carry about 100' of the 10mm if I wanted to keep excess weight out of the bow. 100' of 10mm weights about the same as 200' of 5/16"

(4) However, this would seem --seem anyway-- to restrict my anchor rode. Perhaps, I need to suck it up (I know someone here, in Mexico, is going to provide this counsel... ;-) ) and accept the extra weight for a longer length of 3/8".

(5) In sum, I'm not sure what minimum length of chain I should have, considering where we plan to cruise (S. Pacific, etc.). 100' of 10mm (3/8"+) (and with lots of rope) seems too short chain for the kind of cruising grounds I'm thinking of, to avoid coral and rock abrasion. However, 200' of that chain seems like it would be too much weight. So...perhaps 150' is an acceptable compromise between adequate chain length, and weight to carry in our bow...I simply don't know. Obviously, anchoring system security must take precedence over the inconvenience of extra weight forward... ;-)

(6) Sorry for the long post...