It doesn't seem perfectly reasonable to me. Using "totsufaren" instead of the correct spelling because the 't' sound is already in 'tot' destroys consistency with hinzufahren, auszufahren. And I'm not convinced that 'oi' and 'eu' represent the same sound in German, since 'eu' is a diphthong and always sounds long, whereas 'oi' is a short vowel followed by a glide: [oᶦ].