multi-occurrence DS methods

I have to retrofit a program so that it runs under v5r1 RPGLE constructs
(don't ask), and want to make sure the content of the multi-occurring data
structure is passed in the same way.

Here's how the DS is currently defined...
D DataStructure DS DIM(100) Qualified
D SubAfield1 2a DIM(10)
D SubAfield2 10a DIM(10)
D SubNField3 15 6 DIM(10)

On V5r1, the DIM on the DS line is not allowed.

I think I can achieve the same result by using the following definition...
D DataStructure DS Occurs(100) Qualified
D SubAfield1 2a DIM(10)
D SubAfield2 10a DIM(10)
D SubNField3 15 6 DIM(10)

The difference in the ensuing C specs is that I can not directly access the
DataStructure elements as ...

DataStructure(x).SubAField1 = 'TG'

Instead I must refer to it as follows...

%occur(DataStructure) = x

DataStructure.SubAField1 = 'TG'


Am I correct? If this data structure is passed as a parameter, would the
data passed look the same to the receiving procedure in both cases?

Thanks for any advice.

Tom Garvey