GPRS/RLC in Wireshark?

Hello - [My apologies if this message has appeared more than once; I accidentally mailed it previously from the wrong address.] Is there any easy way to analyze Um GPRS/RLC, encapsulated in GSMTAP at the L1/L2 boundary, in Wireshark? I tried just putting the frames coming into L1 into GSMTAP packets, but Wireshark tries to analyze them as LAPDm. There was nothing obvious in the GSMTAP_TYPE_* values to correspond to Um GPRS/RLC, though I admit that I have not tried other values yet. -- David