If you don't need the "VTL and Cloud Replication" feature, uncheck it on the install. It is what is requiring that .NET install. I doubt you need it since your cluster is isolated.

I just upgraded to the newest Startwind (Version V8 build 11818) and I am no longer able to create thick-provisioned disks using the full disk. I downgraded to Version V8 build 11456 and it works fine. It does not seem to be detecting the correct free space on windows mount points. I did not try it ...