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3x Member w/Anchorage Forces in Sub-Diaphragm

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If anyone can shed some light to the following code exerpt, it would be
appreciated.  Our office has been "discussing" this item for quite some time
now.

UBC Section 1633.2.8.1 Out-of-plane wall anchorage to flexible diaphragms.
Item 5 reads as follows:

5.  The strength design forces for wood elements of the wall anchorage
system shall be 0.85 times the force otherwise required by this section and
these wood elements shall have a minimum actual net thickness of 2-1/2".

Our office has been discussing whether this 3x requirement for the wall
anchorage system, requires all of the sub-purlins in the sub-diaphragm to be
3x's, or just the first bay where the anchorage actually occurs. 

Furthermore, in cases where a Simpson Tension Tie is anchored below the roof
to the side of the sub-purlin, could the thickness of the member be
considered to be the actual depth of the sub-purlin (5-1/2" for a 2x6
sub-purlin)?  This seems to make sense if the code is trying to limit the
potential of splitting of the sub-purlin.

Any thoughts?

Kevin M. Kaplan, P.E.
Associate / Project Manager

VLMK Consulting Engineers
3933 SW Kelly Avenue
Portland, Oregon 97201-4393

Phone (503) 222 - 4453
Fax (503) 248 - 9263
Mobile (503) 799 - 0814