The format requirements in 1026.9(c)(2)(IV)(D) state that the disclosure needs to be substantially similar to the model format. I don’t think a letter format would be substantially similar.
https://www.ecfr.gov/cgi-bin/text-idx?c=ecfr&SID=c61f33bbcc880d96ad116f14b18d7b12&rgn=div5&view=text&node=12:8.0.2.9.18&idno=12