Bob, this is just a hobby for me too. The part about using reversed mounted lens (I believe) is in the 4th edition of the BTZS book. Phil talks about another used that did this. I guess the lens element he describes in the plans is no longer available. I loaned out my copy so I can't give you the page number, but it is in the edition I bought new about 1 year ago.
Originally Posted by BobF
Since the lightmeter sits on a stand, you need to add a magnifier to get that close. Some people also use a series of +1,+2 lens filters to get the proper distance. You also need a way to baffle the light to a small spot. I use a rear lens cap with a hole drilled in it. I am just too lazy to build the stand so I hand hold it. The 35mm lens has a 49mm thread and the meter has a 40.5mm thread, so I bought a 49mm to 40.5mm adapter then a 49mm to 49mm coupler I think it is called a reversing coupler.
I hope this helps please email me if you have any questions.
I would love to own a real one but the Ebay scene is too dangerous for me.