Not sure how to reply to that but I assumed that it would be right under the mast. The point was that on the 38 and 41 the mast is at the front of the salon and at least on the 41 is keel stepped. On the 38 there is a table attached to the mast which makes the salon look very small. None of the interior pictures of the 37 show either the mast or a compression post. Looking further it appears that the mast/compression post is inside the wall between the salon and the head, makes the salon look much roomier. Of course the other option is that the mast is deck stepped without a compression post. Seems highly unlikely.
Thanks, the one we're looking at is a sloop and the picture of the salon does not show a compression post. I wonder if it's hidden in the wall between the salon and head or maybe the bulkhead supports the mast. On our 41 the mizzen mast had no compression post, it was supported by the bulkhead in front of the aft cabin.