I am on area, where my mobile operator (Plus in Poland) provides UMTS2100 and UMTS900 signal, but UMTS2100 is working only as HSDPA 3,6 Mb/s, however UMTS900 is working as HSPA+ MIMO 28,8 Mb/s (category 16). I want to use naturally faster UMTS900, but network configuration is such that the priority is to UMTS2100. So is there any way to force UMTS900 or UMTS carrier 2963 on N900? Actually the only way to use UMTS900 on area, where I am, is significant weakening of the signal, by strong antenna cover, because when UMTS2100 is below -105 dBm, occurs handover to stronger UMTS900, but still after a few minutes phone returns to UMTS2100. Difference in transmission speed between UMTS2100 and UMTS900:
UMTS2100:

UMTS900:

Tests done on N900 connected to computer via USB cable.
@edit UMTS900 upload speed on speedtest is not real, because I use on computer cFosSpeed, that didn't calibrate to HSUPA speed. Real upload is about 1,5 Mb/s.