I'm unsure if this is happening to anyone else or only me. When i TX, it usually get about 54w of power output with an SWR of about 1.51:1. I'm running Expert SDR2 version 1.3.1 Update 11.

Have you tried against a 50 ohm dummyload?
73 LA1IO

Not yet.

Hi, do you use the tuning function from SDR or something else to drive your load? Checked driver level? Input power to the radio,, i.e. voltage and current?

As you can see NO ONE has any idea how or what you are doing to get the 56.3watts so something you could do which might help you get some real HELP is VIDEO what you are doing and stick it on YOUTUBE so then you might get some real help to get sorted, LIFE is easy when you have friends and can see what you are talking about.

Hope this help's
Youtube your best friend for HELP.

So.. i did get my hands on a dummy load. Below are the power outputs recorded.

6m (50.313) 71.4w 1.09:1 SWR
10m (28.425) 81.4w 1.20:1 SWR
12m (24.950) 70.3w 1.29:1 SWR
15m (21.311) 81.4w 1.26:1 SWR
17m (18.126) 86.8w 1:12:1 SWR
20m (14.313) 90.3w 1.20:1 SWR
30m (10.136) 91.5w 1.29:1 SWR
40m (7.173) 98.1w 1.24:1 SWR
60m (5.357) 93.3w 1.28:1 SWR
80m (3.905) 83.9w 1.19:1 SWR
160m (1.840) 75.1w 1.30:1 SWR

My SunSDR2DX exhibits the same behaviour. The max power I get is about 90 watts but typically it ranges between 75 and 85 on most bands. Its been like that since new - just under two years now. I am also using a nist calibrated LP-100A. Cranking the voltage up does not help as it has built in voltage limiter I read. I am using Astron RS35M power supply but I have tried others as well.

Yours looks same as mine. I'll accept that this is normal for the radio and enjoy it!