[galaxy-user] Changing Bowtie parameters in TopHat

My apologies if this has been covered before but I am using Galaxy Main and wonder if, when running TopHat, you can modify the mapping parameters used by Bowtie? It seems that the full parameter list for TopHat pertains only to the reads that aren't mapped by Bowtie (the reads spanning splice junctions). Is there a way to access the full parameter list of Bowtie through TopHat? Or perhaps run Bowtie directly, then feed this into a TopHat run? Thanks, Jeremy