V8 does not seem to handle extending surface edge (extendsrf) well if there are internal trims, there lost. Put the same surface in v7 works as you would expect.
V8 extends the edge and removes all the trims
In the attached file extend any outside surface edge to see the issue.
ExtendSrf.3dm (411.8 KB)
Updating this with some pictures.
Currently the workaround in to extendsrf without merge,Join, then MergeCoplanarFace
Sample surface
Extend an outside edge of the surface
Extendsrf V7 (as expected)
Extendsrf V8 (loses all internal trims)
Last one
Extendsrf V8 (with merge turned off) This one works as expected
Ouch.
Same in V9 WIP.
Thanks @ken_miller for reporting
RH-83317 ExtendSrf removes trims
404…
I’d like to know if the ExtendSrf removes trims issue will be cured.
both the link and the issue have be fixed 
That’s the important part!
Thank you Gijs.
Look forward to the release of this update.
Thanks, Much appreciated
