I do not have a HVL-F42AM to try, Bob. Only the '36 and the '56 ... so we are out of luck with me trying to duplicate it.
Remember, the '56 and the '42 really do not necessarily play well together. The '42 was really designed to be partnered to the newer '58 flash. As you have already attested, I have it working with the '36 and the '56, myself.
You might just try looking for a
'36 on ebay (<- click this) or in one of the local camera shops. You should be able to find it cheap enough. I got mine, USED, for around $80
