Oh, I posted a link above
GIE-TEC Assembly and Soldering Frames) with prices on that page. Says 44euros for big frame BL142043. BL149241 = 6.20euros and BL149242 = 1.50euros.
Is the BL149241 an extra rail? And the BL149242 is those spring clips for your greenouse ?!
30mm legs will be fine then for long resistor legs hanging down then. (average resistor leg length is less than 30mm length, not incl. extra space of elevated pcb in holder) The legs look smaller in the pics.