Roll Cage Questions

Hi trying to find answer to the following questions for building a 10 point roll cage but I can not find anything via google. Hoping someone here can help.

1. With a backhalfed ladder bar car. Does the main hoop need to be welded right on top of the ladder bar crossmember? Or can the main hoop of the roll cage be welded directly behind the ladder bar crossmember. see pic below

2. When is it necessary or a good idea to have the rear frame rails for the roll cage braced with an x between them instead of no brace and just straight back only?

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