How can I use two different fixed point datatypes in stateflow

I'm using stateflow and in one state I'm computing two equations. One (V_comm1) gives a fixdt(1,126,55) as output an the other (V_comm2) gives fixdt(1,58,12) as output. When I use the following operation (V_comm1 < V_comm2) I get the following error:

Type mismatch: embedded.fi {sfix58_En12} ~= embedded.fi {sfix126_En55}.

When I change the Datatype in the Model Explorer of V_comm1 to (1,126,55) in order to have the same size as V_comm2 I get the following error:

Inferred type ('embedded.fi (sfix58_En12)') for data 'V_comm1' (#182) does not match specified type ('embedded.fi (sfix126_En55)')

How can I solve this problem? Many thanks in advance!