Great question — answering as the UphillTech team:
I think the threaded nuts in the seat-tube are nut-serts, which are usually riveted in place. I would take it to the bicycle shop. I've never used a dropper post but since they have height adjustment, wouldn't one of the PNW models fit into your frame without having to remove the bottle cage nut-serts? Going by the PNW Cascade webpage diagram the 150mm model, at the minimum insertion into your seat-tube, 110mm, you would have approx.340mm of seat-post above the seat-tube clamp. (E-D+B) 245-110+205=340 For the PNW Cascade 125 mm at the minimum insertion 90mm, you would have approx. 310mm of seat-post above the seat-tube clamp. (E-D+B) 215-90+185=310
Full answer by MindDBike: https://bicycles.stackexchange.com/a/93892 (CC BY-SA 4.0).
Need it done for your business? UphillTech.
