For Old Hungarian, I used the four gospels from the Hussite Bible, and I counted long and short vowels together. The top three letters break down as follows:
Like Latin and Rohoncian, the most common letter in Old Hungarian is more frequent as an initial than as a final, while the third most common letter is more frequent as a final than an initial. Like Latin, these two letters are e and t, respectively.
You might wonder why, if there are around 1,000 glyphs in Rohonc, I am comparing it statistically to alphabets instead of syllabaries or ideographic systems. The reason is that the most frequent glyphs in Rohonc are roughly as frequent as letters ought to be. Among Latin syllables, for example, the most common syllable in the Vulgate version of Genesis is et, but it only accounts for 3.29% of syllables. The most frequent Rohonc glyph is C, and it accounts for 12.9% of glyphs, putting it in the same ballpark as the most frequent letters of alphabetic systems.