I picked up some candidate parts of the PR2/PR3 payloads whose materials could change from A6061(-T6?? --- it would be nice to be indicated clearly by VIS...) to A5052-H112,
and asked the manufacture company about the cost reduction.
Those parts are for box structres of IM and IRM.
Hope the oreder can be done soon (in low cost!)...
Some information
http://www.zairyo-ya.com/info/zaisen_tebiki_2.html
http://www.labnotes.jp/pdf2/aluminum.pdf
http://www.toyo-success.co.jp/product/characteristic_a.html
http://fa.misumi.jp/product/plate/prty.html