I have been operating off the impression that the receiver has "several other holes" rather then just a couple extra. Hence my recommendation to consider having them welded. To me a bunch of screws in a small area is going to look messy but I guess this is up to ones own personal taste.
Whatever enjoy this rifle for what it is. A great 22 from times past that will probably never be duplicated again.
Just to add a little extra info here; I have a Remington Fieldmaster Model 121 from the same era and this is another excellent quality 22 pump.
Jim
