I've triedThoragoros tutorial but never worked for me. Anyway I didn't pay much attention since I always make these changes through startpos. After Mefistofeles post I checked again and I can confirm the following:
1. Changing only db table is not enough to change the starting building slot (I repeat that is from my tests, maybe Thoragoros can do this.)
2. You can change the slot with the classic way we know from ETW, as Mefistofeles followed. In this case everything works fine.
3. Now about Helsinki: it is still referred as commercial center but this probably a cosmetic issue and not a real reference, because it can be upgraded to next industrial levels (I do not agree with Mefistofeles in this point) and the industrial effects are present (income, industry research techs, etc.) Anyway there is a way to fix this but you have to make changes in regions.esf file. For the moment there is not a stable Editor for regions.esf. In the next images you can see Helsinki as industrial center after both startpos and regions files have been changed. Second image is without regions.esf changes.