I am affraid that after two days spent on custom field mapping issue I have come to the same conclusion as you did a while ago e.g. that both mentioned resources are either missleading or the proposed solution is not functional. Maybe the proper world would be useless.Not to just complain I would like to published my finding: by editing nameLookup-VCARD.xslt file I was able to achieve certain control over what is being displayed when the lookup is made and what is being transfered to contacts on mobile device when the contact is being copied to it.
Frankly speaking it is not reliable at all. For example I was able to show OfficeFAXPhoneNumber but when the contact was copied localy the wrong field was used (on Win Mobile) and I did not manage to fix it. I completely failed to either show or copy Web Site information (WebSite field).
By the way have you managed to solve the issue somehow in the meantime?