You mean Morel brand lifters?
"Link bar lifters" which include Morel. Others have complained of other brands as well.
If the "Tech" says the lifters have a maximum recommended limit of 5,600 rpms and if your rpm limiter is set to 6,800, you had the potential to surpass the 5,600 rpm recommendation.
It isn't a very common discussion but it is mentioned enough times to suggest investigating further as a potential pitfall.
In my own personal experience I have found that it is not unusual for one individual to have isolated an issue and determined a viable solution, generally unknown by the larger group. In fact, my experience tells me to look for that person, that they are there somewhere.
The mentioning of a "valve float situation" is distracting and should not have been mention if it was the rpm's alone that likely caused the failure in my view.
I would use the word, irrelevant to describe it's mentioning.
I don't know enough about the weight of the valve train components to know exactly where to expect valve float with those springs.
I would think also that if it is an accurate analysis that you are getting valve float at as little as just over 5,600 rpm with 450 pound springs then I would start to be concerned about the push rods also.
Somewhere in this thread I thought that I read that there was a recommendation to go to a solid flat lifter cam and lifters and how absolutely shocking that it could use more duration and closer center lines? I don't remember who it was that suggested that?