fixed point scaling in simulink

Hi, I have a fixed point block for the dot-product. Currently the input
data is of type sfix(13) with scaling at 2^-3. This works nicely.

However, the output is set to "inherit via internal rule" but this
outputs at sfix(26) which is a bit more than I want.

Is there any way I can change this sfix(26) to sfix(13) without
overflowing the block - i.e. what is the requirement on the scaling to
make sure the answer stays the same (I'll obviously lose some
information, but this will probably be some low power noise).

Cheers,

Phil

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