Wowza has a few properties to control the maximum UDP Packet size in regards to RTP Streaming:
Under Streams/Properties in Application.xml:
<Property>
<Name>h265MaxPacketSize</Name>
<Value>[VALUE]</Value>
</Property>
<Property>
<Name>rfc3984H264MaxPacketSize</Name>
<Value>[VALUE]</Value>
</Property>
<Property>
<Name>rtpAACMaxPacketSize</Name>
<Value>[VALUE]</Value>
</Property>