I have just completed assembly of a 9 stall Heljan Roundhouse except for weathering and some finishing detail. This was done with the base kit and two add on stall kits, each with 3 stalls. This kit has been around forever and I had a 3 stall version of it on my old layout. Overall, I am very pleased with the result. I did find that despite my best efforts, I had to fudge a little to get it to fit.
Because of the size of the roundhouse, I made the decision to assemble it in place. After positioning the base, I installed the lead tracks. Despite precisely measuring from the center of my turntable to to the front and rear of the roundhouse according to the diagram on the box, I had to bend the lead tracks to the outter stalls slightly to get them to line up. I probably could have fiddled with it until all the stalls lined up perfectly but decided the bends wouldn’t be noticable from any viewing angle so I left it where it was. I also found that each of the back walls was slightly longer than the base which meant that by the time I got to the last stall, the back wall had to be trimmed by about 3/32" to allow the side wall to line up flush against the base. Many of the roof joints had gaps of about 1/32" which I plan to disquise with strips of “tarpaper”.
As it is, it is a very impressive looking structure. When I get around to learning to use the new 5 megapixel camera I got for Christmas, I’ll post some pictures. This will also give me a chance to put the finishing touches on the rest of my transition era engine terminal.