controlling indentation on individual XSLT steps?

Dear xproc-dev,

I'm executing a pipeline that includes two consecutive XSLT step where,
outside the XPRoc 3 environment, I control pretty-printing with:

<xsl:output method="xml" indent="no"/>

<xsl:output method="xml" indent="yes" suppress-indentation="form stressed"/>


It looks as if XProc overrides the serialization settings in the XSLT and
indents the output, and I don't know how to override that in different ways
for the two pipelined XSLT steps. I suspect that the unwanted
pretty-printing is being imposed by XProc because I get pretty-printed
output from the XProc, but when I run the two transformations outside the
XProc environment, I get the more fine-grained control that I need.

The steps currently use default connections, that is, the output of a
previous step is the principal input into the first XSLT step, its output
is the input into the second XSLT step, and its output undergoes further
processing. If I've understood correctly, I can use <p:with-option> with a
map to set serialization parameters on an output port, but since I'm
connecting default input and output between the steps, I don't know where
the serialization should be specified. Would someone be able to point me
toward an explanation? Thank you!

Best,

David