kana usage - Sokuon Diacritic and Wabun Morse Code

I have created a geocache puzzle based on Japanese Morse Code (Wabun Code).

The final coordinates that I translated are: N 43° 09.725 W 077° 26.688

I broke this down as follows:

N    4      3   °     9  .     7         2     5  '
kita shijuu san jisuu ku chobo nanahyaku nijuu go fun

W     7       7      °     2     6    .     6        8       8     '
nishi nanajuu shichi jisuu nijuu roku chobo roppyaku kyuujuu hachi fun

I wasn't sure about the terms for: north, west, degree, decimal, or minutes; but I thought it was probably passable.

I broke these out into kana:

キタ / シジュウ / サン / ジスウ / ク / チョボ / ナナヒャク / ニジュウ / ゴ / フン
ki ta / shi ju u / sa n / ji su u / ku / cho bo / na na hya ku / ni ju u / go / fu n

ニシ / ナナジュウ / シチ / ジスウ / ニジュウ / ロコ / チョボ / ロッピャク / キュウジュウ / ハチ / フン
ni shi / na na ju u / shi chi / ji su u / ni ju u / ro ku / cho bo / ro long(p) pya ku / kyu u ju u / ha chi / fu n

And then mapped those kana to Wabun. I even updated the Wabun wikipedia page to combine the dakuten and handakuten diacritics and other digraphs. That was the toughest part for me to get in all my research.

You can see the page at: http://en.wikipedia.org/wiki/Wabun_code

This is where my real problem starts. My research showed, roppyaku should be written as ロッピャク, with the sokuon (small tsu) used to mark the double "p" consonant.

For example, Pocky (a Japanese snack food), is written in kana as ポッキー

From what I could find of Wabun, there are only diacritics for Dakuten (◌゛), Handakuten (◌゜), and Long vowel (◌̄). There doesn't appear to be any code in Wabun for double cosonant.

Unable to answer this question, and not wanting to use the "wrong" form of 600 like this...

ロ     ピャ              ク   
ro    pya             ku  
•-•-  --••- ••--• •-- •••-

I went with the incorrect, but "understandable to westerners" form of 600 like this...

ロ     ク     ヒャ        ク   
ro    ku    hya       ku  
•-•-  •••-  --••- •-- •••-

What would be the correct way to represent 688 in kana and translated to Wabun?

The only real Wabun information that I found was on Wikipedia. All other references seemed to be based off of the Wikipedia article. Is there a way in Wabun to represent the sokuon diacritic that isn't represented in the Wikipedia article?

Answer

The pattern is quite clear: digraphs are written as if the 'small' character were full-sized. Hence for example ギョ is written -•-•• •• --: キ + dakuten + ヨ.

Thus, write the ッ as ツ.