Increased program size after change SDK version (1.1.4 to 1.2.0 beta)

I just updated from SDK v1.1.4 to v1.2.0beta and recompiled a 920xt data field without any source code change. The program size increased from 12.4KB/16KB to 14.9KB/16KB (see attached screen grabs). And worse, while the 1.2.0beta version runs, as soon as I start the FIT data simulation the program quits with an out of memory error. Perhaps branching to an area of code that loads more resources(?) as my code doesn't do much until HR data is not null.




With FIT simulation off, but program running in simulator, console reports:
Copying file.... 100% complete
File pushed successfully
Connection Finished
Closing shell and port
Found Transport: tcp
Connecting...
Connecting to device...
Device Version 0.32.1Device id 0 name "A garmin device"
Shell Version 152253


Then when I start FIT simulation
Copying file.... 100% complete
File pushed successfully
Connection Finished
Closing shell and port
Found Transport: tcp
Connecting...
Connecting to device...
Device Version 0.32.1Device id 0 name "A garmin device"
Shell Version 152253Out Of Memory Error


What's going on here?
a) yes code has not been optimised and is close to max 16KB but surely it shouldn't crash.
b) do I just have to accept this and optimise code or did I miss some setting or other reason?

Thanks!