If a trustee determines that an allocation between principal and income required by section 469.437, 469.439, 469.441, 469.443 or 469.449 is insubstantial, the trustee may allocate the entire amount to principal unless one of the circumstances described in subsection 3 of section 469.405 applies to the allocation. This power may be exercised by a cotrustee in the circumstances described in subsection 4 of section 469.405 and may be released for the reasons and in the manner described in subsection 5 of section 469.405. An allocation is presumed to be insubstantial if:
§ 469.435, RSMo