Rapid Rectinear lens -- front or rear elements for doubling the focal length

[Bill_1856]

It's a Centar Series 2 convertible lens of about 11" focal length. Would it be better to use the front or rear elements to double the focal length?
(Absolutely Gorgeous image used normally!)
Thanks.

[Tracy Storer]

Off the top of my head, RRs are symmetrical, so either cell should do. Generally, you're better off usng single cells behind the stop, but if extension is an issue, you can go in front.