hope your eyes are really good to work with the giffin grip. make sure all three grips are set at the same place in the row of notches. if it seems to not be round when you trim things, check that again.
birdnsong, if freezing weather would not hurt your water supply, there is no reason not to run a pipe carrying fresh water out to your studio. you do not have to drain the sink into a sewer at all. mine is drained into a 55 gallon drum and i usually use a bucket inside the sink to catch clay and dirty stuff. that bucket gets tossed out the door onto the yard. very little clay is in there because i work fairly clean and use very little water for throwing. walking the few steps outside to toss the water out is good exercise. only once did i do the silly "hold-onto-the-bucket-too-long" and splashed slurry onto the concrete step, my shoes, my pantlegs and assorted other things that i then had to wash. ( you have seen the people on TV who do not let go of the rope hanging over the river.)
the plastic 55 gallon drum is on its side outside the studio with the drain pipe dropping into it through a hole drilled to fit. the bung hole of the barrel is on the high side of the end and a piece of insect screen is stretched over the bung hole. cannot even see the water that may have collected in the bottom of the barrel in 3 years of use for each winter, it is so low.
the good part is that the sink is a deep one, a janitorial kind that allows me to put buckets inside to wash them off. no outside hose needed. there is enough dirt tracked in by the dog, i don't need wet mud added to that.
wherever you live there is a government agency to ask about how deep a water line needs to be buried to avoid freezing. if it is a reasonable depth, go for it.
Mitch Lyons has done this for years. i know he is on youtube showing how it is done. he did a demo for our guild meeting a few months ago. the fabric he uses is a heavy grade of brand name Pellon. it is sold in fabric stores for lining jacket lapels and other stiffer items of clothing made by seamstresses or tailors.
he has laid down a very thick "sheet" of clay onto which he puts various colors of slip. once he is satisfied he puts the pellon on top and rolls the color into the pellon. the resulting print is then framed. watch the trick of the mat around the edge in the video.