Umex RM2 miniPCI (Prism GT) + WRAP2.C + Pebble = radio performance issues

Hi Folks,

First time poster, who drew a blank with the list archive and googling.

I'm not a strong RF guy so am feeling my way in the dark and if this 
isn't the right list for this sort of question pls refer me.

I've got my prism54 drivers installed and working but have noticed some 
performance differences with my previous AP kit. The kit runs in quite a 
noisy environment with other APs in range.

WRAP2.C + Umex RM2 miniPCI (PrismGT) gives very meager signal strength 
when configured like this -

> IEEE 802.11b/g  ESSID:"wrap"
>           Mode:Master  Channel:10  Access Point: 00:0C:76:70:3E:BA
>           Bit Rate=2Mb/s   Tx-Power=31 dBm   Sensitivity=20/200
>           Retry min limit:8   RTS thr=2347 B   Fragment thr=2346 B
>           Encryption key:off
>           Link Quality:0  Signal level:0  Noise level:191
>           Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
>           Tx excessive retries:0  Invalid misc:0   Missed beacon:0

My old Soekris 4511 + ZCom Cardbus XI-325 (Prism2) gives me excellent 
signal strength when similarly configured -

> IEEE 802.11b  ESSID:"soekris"
>           Mode:Master  Frequency:2.437GHz  Access Point: 00:60:B3:8B:E4:2A
>           Bit Rate=2Mb/s   Sensitivity=1/0
>           Retry min limit:8   RTS thr:off   Fragment thr:off
>           Encryption key:off
>           Power Management:off
>           Link Quality:0  Signal level:0  Noise level:0
>           Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
>           Tx excessive retries:167  Invalid misc:3   Missed beacon:0

My questions are-

Is it possible to set Sensitivity with Prism54 drivers (or is this more 
of an antenna gain issue)?

Am I right to believe TX Power cannot be set by Prism54 drivers?

Will reducing RTS and Fragment settings on WRAP/Umex setup to match the 
Soekris/Zcom setup, help reduce frame collisions and improve range and 
throughput?

Or is this about the best performance I can expect?

Thanks

Colin