This is my summarized opinion of existing CoQ10 clinical data. I am not in the medical industry but do analyze data professionally. I only provide this as I believe it my be helpful in answering the question of dosage volume. I hope that answers to this thread will be helpful to others and I will continue to update the thread with our experience.
This trial - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3136634/ - documents an 8.5% increase in strength measurements over a 6 month period for 5 to 10 year old boys taking CoQ10 (Myoquinon Q10 from PharmaNord) who were also on a stable regimen of prednisone. They monitored the boys for 3 months before giving CoQ10 to distinguish between strength increases from prednisone and CoQ10. They sought to reach a serum CoQ10 level of 2.5 μg/ml.
The 8.5% increase in strength did not decrease the time required to complete timed tasks. This is not a miracle supplement but might contribute to the slowing of progression.
CoQ10 is readily available. However the blood testing they used to monitor serum levels of CoQ10 are not likely to be accessible. They used a lead in dose of 400 mg per day increasing in steps of 100 mg until they reached desired levels. The required dose to reach 2.5 μg/ml was highly varied. Final doses ranged from 8.7 to 48.4 mg/kg.
For my 28.6 kg (63 pound) son that dosage range would be 249 mg to 1,383 mg. Another study established that adults could tolerate up to 900mg of CoQ10 per day for four weeks. My son is perhaps 1/3rd of the weight of those adults.
My thinking is that I will give my son a 400mg (14mg/kg) dose that we would lower if side effects are seen.
As a side note, my limited opinion is that Ubiquinone is preferable to Ubiquinol as the former has more clinical testing. I do not have an opinion on ubiquinone versus idebenone beyond the greater availability of ubiquinone making it where I choose to start.
I am hoping that others will be able to share their experience and suggested dosage.