I will admit I didn't think about it too carefully, or go and read the specs. I just recall that the default settings in Multitech were different to the defaults in RN2903. Its worth a paperwork exercise to review all the settings on both sides and check they match. There are too many to just try bigger numbers and see what happens.
It may be that the Multitech parameters all get over-ridden by the TTN integration, I don't know, but still worth checking for all the same reasons.
In the RN2XX3 documents, the defaults are all listed under the various "mac get ..." commands.