At first glance, the Venolia engineer's comment regarding their pistons NOT failing may seem a little flippant. But it probably is not.....
Going through records and recollections of our engine failures, we came up with several "piston failures" - however, the pistons themselves were NOT the cause of the failures.... oiling to the wristpins was compromised on more than one occasion, resulting in the seizure of a wristpin - the evidence was there on the "unfailed" pistons..... seizing a rod bearing which resulted in side forces so great that it tore the bottom of the piston out sideways (as well as a piece of the cylinder)....etc..... some of the problems were "cured" by getting rid of our drag racing engine building ideas as well as upgrading to a new "priority oiling style" block and fitting our oil pressure relief system to a remote location at the opposite end of the engine from the pump (in hydraulicspeak, it is technically a sequence valve when used that way).
The problem that you have, though, is that there are no upgraded priority oiled, high nickel alloy, flathead blocks that come with "CNC" pre-porting available (are there?).... and when you take out a flathead block, it is pretty much the same as, to us overhead valve racers, also losing both heads.... so you are right in being extremely concerned about any and all safety aspects.
When we were having problems with our short stroke big block, we had a fairly lengthy discussion with a NASCAR engine builder..... his words, at the time, were that, with piston technology as it was at that time, pistons would live well at a speed of not more than 4800' per minute.... implying an engine rpm of 8800 or so, if equipped with a 3.25" stroke....I know now that they have exceeded 4800 feet per minute in NASCAR (like up to probably 5000 feet per minute).... keep in mind that this is for engine longevity in the 500 mile range. He alluded to drag racers pushing that number up some.... he did not commit himself on the idea that Bonneville racing could also push that number up some....
What I will say is that there are several good tips so far about keeping your engine together..... and, long (as you can get) rods is a way of not overly side loading the wristpins and pinbores (as well as the skirts and cylinder bores) which usually rely on "drip and/or splash" lubrication that can be spotty....
As an aside here, there used to be a guy up our way who was a top alcohol drag racer....He had no big dollar sponsors and he was runing iron '92s.... his ongoing lament was that he could not afford the cost of any of the Donovan 417 blocks that he had come across for sale at the time.... and that good iron '92 blocks were getting nearly impossible to find for any price.... He fabricated several 392 style blocks out of plate steel and had them furnace normalized prior to machining them...The were NOT super light or anything but they were bullet proof, so to speak.... and he leaned hard on those engines for a few years..... He eventually got some sponsoring and bought a couple of K-Bs though....
So. it got me thinking...... if a guy up in Canada can fabricate a 392 hemi engine block, what is stopping people elsewhere from fabricating flathead blocks...... and putting in priority oiling, 5 bearings, KickA** porting, rerouted and/or better cooled exhaust ports etc....?