Jim McCoy wrote:
The only problem I see in training in other arts is that it will slow your progress in each.
Oft stated, but never proven.
Over the long run it has been my experience that cross-training (even from the beginning) enhances progress. If you take a look at studies done on bi-lingual children you see much the same thing - apparent slow-downs in linguistic skills in the early years, but greater achievement in the long run. No downside at all.