Sorry for my late response. I had some unexpected, personal leave.
1. MSS clamping
I tried a range of values from 1000 to 1500
–> no meaningful change, i.e. low and fluctuating speeds
2. Phase 2 encryption
I tried all values of AES-GCM
again, no meaningful change, i.e. low and fluctuating speeds
3. Turning off hash algorithms
Do you mean in Phase 2 only?
Hash algorithms cannot be turned off, so I chose SHA1
4. powerd
this is set to Enabled and hi-adaptive in all contexts
I will have another connection available in a few days will be able to test using virtual endpoints, using the community edition, instead, running server-class CPUs
thanks for your assistance.