*For me it was
just:
- Created a 16 sided cylinder 192x192x128.
- Moved all the points in one of the bases at the same time in the same plane as the base is to make the ''curve'', with the vertex editor tool.
- Repeated the previous steps another time and joined both cylinders to get one fourth.
- Cloned and rotated 90� that structure 4 times and joined the pieces to create one tube.
- Cloned and rotated 45� the finished tube 7 times.
And got
this.
I didn't even check if it was on grid, calculated a single thing or tried to make it look good thats why i only used two pieces per 90�. I was only checking if it was doable so made it simple.
All looks OK in game and the compiler didn't give a single complaint so i didn't bother. Maybe you encountered problems because you made it detailed, hence the need for calculations.
* About Trenchbroom i don't know much, but i suppose that for this basic operations is the same as any other editor and from what i heard it supports map format 220 so no problem there either. I don't use JACK much either, except for Quake 2, just WC from 1.1.2 to 3.3 since i began mapping, which is similar.
Mainly because till a few years ago i only knew of WC 1.1 and QuarK as back on 198x-199x everyone in the city with a computer depended on what the rich guy or guy with family abroad or in a really big city got for almost every software we had.
* About carving (subtracting from one brush using other), is one of the only three tools WC1.1 had: Create cubes, wedges, cylinders and spikes was one, carving the second, and hollow (to create hollow boxes) the third.
It was quite limiting that's why it surprised me the spiral staircase on grid back then. But thanks to the limitations it has i had fun making some crazy things till i hit the editor's limit on what could be displayed in-editor and had to put the
most of it apart.