Ted,
Another thought on this, other than what thirdeye had already mentioned is this....
D1.1 :2004 paragraph 5.13 Conformance with Design says..." The sizes and lengths of welds shall be no less than those specified by design requirements and detail drawings, except as allowed in Table 6.1. The location of the welds shall not be changed without the approval of the engineer.
Table 6.1 Visual Inspection Acceptance Criteria Item(6) undersized welds
catagories for Statically Loaded Nontubular, Cyclically Loaded Nontubular, & Tubular (all loads), "the size of a fillet weld in any continuous weld maybe less than the specified nominal size (L) without correction by the following amounts (U):
Specified (L) is less than or equal to 3/16 = allowable decrease (U) is less than or equal to 1/16. [Note: Other sizes of fillets/allowables are listed but I didn't include them]
In all cases, the undersized portion of the weld shall not exceed 10% of the weld length...."
As for the maximum size allowed... hmmm, The code specifes max sizes for lap joints(paragraph 2.3.2.9), but if the extra size doesn't interfere with the usefullness of the part, I'm not sure there is anything other than heat input to limit the max size allowed, unless I'm missing something somewhere.
Hope this helps,
John Wright