The following definition in mesh_types.h appears to set the max length to 14.
#define gMeshMaxAppCustomDataSize_c 14
I tried changing this value but it appears to be set to 14 in the mesh binary. Mesh_SendCustomData() will return an error if meshCustomData_t.dataLength >= 14 regardless of the gMeshMaxAppCustomDataSize_c value.
Is there any way to increase the max size or is this it?
That is the maximum size, please remember BLE Mesh works on Advertising packets.
Yes, data size is 14B but usually 1B will be the opcode, so at the end you have 13B left as real application data.
Thanks for the help. Does the use of advertising packets also affect the reliability of the packet delivery? ie is there a guarantee of delivery or is it maore a fire and forget with the possibility of the packet being stepped on? Please see my question regarding packet loss with BLE Mesh from a couple of days ago. https://community.nxp.com/thread/441389