PSK31 text lower or upper case?

[ve3ibw]

Is the KX3's PSK D support for sent/received PSK31 text upper or lower case?  I ask because the VFO B display on the KX3 shows only upper case letters being received.  Also, when I send lowercase through Hamlog and the Piglet from Pignology, the KX3 shows only upper case letters.  PSK31 best practices indicate that to achieve better message content throughput, use lowercase letters as often as possible.

Regards,
Brian
VE3IBW