3/4" blanks are OK for the PSI closed end kits, if, as Kyle cautioned, you drill carefully and accurately on the center. . I have done this many times.
I know that the instructions for the closed end kits are not well written and there are some inaccuracies. . There are several different drilling operations, and you have to think things through carefully before you drill the closed end holes. . Also, the design of the cap finial that holds the clip is not very well described and the instructions are a bit "off". . I know there are different closed end kits, and I forget which one it is that I had these problems with. . But I do think it was the closed end Majestic Jr.