Which is more important, straight mast or balance shroud tension?

[Kenneth K]

What about the tension of the stay from the cabin roof to the mast step. Is there a tension measurement on that one?

The interior stay between the mast step and the cabin roof is related to running rigging, not standing. On a keel-stepped mast, tension in the shrouds/stays doesn't affect the cabin top, but all those lines anchored to the mast collar (when tensioned) pull upward on the cabin roof.

I suppose the stay should be tight/firm when there is no load on the mast collar, but not enough so that it pulls the cabin top downward. Then, as loads are added to the mast collar, the tension on the interior stay will increase correspondingly, in response to the upward forces.

 

[Dave G.]

I would start with snugging it up and a half turn then put a couple halyards on a winch tighten them up and check for any lifting. Adjust as necessary.