Mast splice

[pda1964]

Working on a mast splice for an Isomat ng70. According to sparcraft, the splice insert needs to be 32 inches total length with 16 inches in each section. What I've found on rivets recommends 4x dia (3/16" rivets) to start pattern and 8x dia for rows with rows staggered. But this gives me around 240 rivets total in the splice. 60 rivets per side for each end. That seems like a whole lot. Is this reasonable? Sparcraft doesn't give information on rivets but the picture seems to only show like four rows from end of splice. Just trying to get this right and any help is appreciated.

Paul