I'd be inclined to cut it into 3 pieces and root each one in a citrus tall pot.

Some clumps in the display garden I purchased are probably 15 years or more since last division, huge 3 foot across at least, and still blooming like mad. Others are much smaller, obviously divided more recently, and barely bloomed. I think it just depends on the cultivar, your soil composition, nutrient conditions, water, etc. It makes sense. The density of roots vary greatly by cultivar so if they are so bound up that they can no longer reach the nutrition they need to thrive, they will show you by declining in bloom.

From what I've seen (never done it myself), you should be able to root larger cuttings (truncheons) of this plant as easily, or maybe more-so, as smaller cuttings. If there is significant new growth at the tips, you may have to prune back to firmer wood. A moisture tent and rooting hormone should improve your odds.

I made lined drapes with pleating tape a long time ago. It was murder because I bullheadedly didn't set up properly on a table, just used my sewing machine cabinet and let the fabric fall all around it. Since you obviously have more brains than I did then and will buy a table, I'm sure you can do it. They really are not hard to make if you support all the fabric on a table. Mine turned out well. If I were doing it today, I'd move the machine head to my dining room table for a few days. That's what I do nowadays when I make something huge like prom or wedding gowns. Sherry