The inter-web is a wonderful place, but can also be populated with an abundance of trolls who deal in speculation/rumor/outright falsehoods. Sorting real experience from opinion can be tough, even when folks claim to have "experience". That being said, MII front end kits are similar to '32 glass bodies, lots of sketchy people got into the "business" of selling the stuff when the market was really hot a few years back. Odds are there are some crap parts out there built down to a price instead of up to a quality standard. As Tom said, a name brand product with a long history is a safer bet. Add to that the questions of who installed it, what their skill level is, and even do they know how to weld properly? Further the arguments over the years about whether a "Pinto" based suspension was heavy duty enough for application X. First the Pinto/MII was heavier than many think, some versions near mid 3000# range, and that was with all of the engine weight centered over the suspension rather than mostly behind it as in most rod applications. And then there's the matter of what gauge material was used in the fab of the aftermarket pieces. Lots of variables to consider.

I've been a Heidt's fan for years because their stuff is proven and looks good to boot. They've worked for me, not interested in any other brand. Others have demonstrated their products are well made, I just don't see a reason to deviate from a known, successful product.

As for the setup you pictured, there probably isn't much useable strength to be gained from capping that hole, but as Roger said, what can it hurt? If nothing else you would eliminate a cavity that will catch all manner of road debris