Yes indeed, the SDCCH UL and DL multiframes are offset by 15 TDMA frames. The starting point is different 🙂
I’m not sure why you measure less drops when you increment the T200. Are you sure the improvements occur only in bad RF conditions ?
Default value was 145ms, which other values did you try ?
Are we talking about the T200 for supervision of SDCCH SAPI0 ack, or for SDCC SAPI3 ack ?