Sent SendCutSend another job. Exhaust support bracket. They got back to me the same day advising my files were "not optimal." To their credit, they referenced my AC bracket job file (below) so it was possible to see what the issue was. Too many nodes. This results in a rougher laser cut than were the shape made of minimal nodes. They emailed me my file from the AC job and one they modified...
My file. On the aluminum parts I received, edges were indeed rough on the curved cuts but not objectionable to the point where the parts were "bad." The straight edges of the AC mounting parts were noticeably much smoother. I emailed SCS asking if that aluminum had been water or laser cut. I thought it was water because of the way it looked. Was laser. So they schooled me...
Above is their adjusted file. Minimal nodes.
As a result of this node-business, am looking into Inkscape and Onshape.
Took my node-abundant Tinker file for the exhaust support bracket into Inkscape and traced it using their vector tool. It's apparently possible to go from Inkscape to SendCutSend. Instead, I brought the Ink file into Onshape (image above) to see if & how that worked and to use Onshape. The vector points & handles from Inkscape remained workable. (Vector stuff is akin to Adobe Illustrator but the interface of both Ink and Onshape is clearly 3d modeling based.) Made adjustments in Onshape using various layers. Saved the file for SendCutSend as a DXF. Thought that was the end of it. Wasn't. Found that ALL the hidden layers were included in the DXF file. So trick here was to trash---not just hide---all unwanted layers before saving to export a "surface file" for laser cutting.