i honestly think that mold works better for impactor,minus the hands.just keep in mind,it's quite the head ache to get rid of the spring loaded shoulders.i also have the same hulk mold for "impactor,i even went so far as removing his right hand and adding a light up bionicle spear.once i got the the fore mentioned shoulders,he's been shelved since,minus right hand and all
but if you're interested in roadbuster as a "bigger" bot than universe 2.0(cdf hotshot),i'd say try to find the marvel captain america mold.it fits it really we'll,along with a kit that's available from a member on tfw that'll make him into r/b that much more.the last one here i seen that blew my mind was done by autobotx23.
maybe try hitting him up
,you never know till you ask right?