install cowl blocks.

['29wagon]

i've acquired a set of decent wood base blocks for my '29 cowl both are slightly thicker than the metal channel so i plan to sand the flat side a bit to fit. i can't tell which but either the top side or bottom side of these wood blocks are tapered, concave maybe to ease the install. if some one can inform me so i'm not to botch this procedure i know they need to be tight.