The chosen level doesn’t really matter as there are insufficient numbers available of any section of rider ability to offer equality across the current number of teams.  Doubling up isn’t actually killing the sport, after all it’s keeping clubs alive due to the sharing of riders. It is however removing any real opportunity for growth because as you say the sport needs credibility and doubling up acts against that concept.  For speedway to grow in the UK, what’s needed first of all is some pruning to give eight full time professional clubs with the remainder running on a (lower cost)semi-pro basis.  Unfortunately there’s too much self interest involved by promoters to make this an immediate possibility hence unfortunately the demise will in all probability continue. 

Business Studies... how not to run a business 😂

Coventry team managed by Hans Nielsen Chris Harris Jody Scott Leon Flint Luke Harrison Dan Thompson Ashton Vale Senna Summers

It may be the case at this time and the situation will only get worse until those riders starting out and those still learning their craft are given more track time. To continue to deny those on the bottom rung of the ladder the opportunity means the sport will end up with the self fulfilling prophecy of of end of UK speedway as it was once known unless the intention is to get the overseas nations to train these riders and bring them to the UK to fill team places at higher costs and result being you maintain the status quo of not enough British riders coming through the ranks. Something has to give and people need to look elsewhere if the ambition is to watch world class riders week in week out, UK speedway cannot afford to entertain these guys or continue to use doubling up as a long term option.

Depends what levels you set the leagues and how many riders in a team I guess.  doubling up is killing the sport in this country. We have to either limit it to uk residents first and then get rid or the whole system in say 5 years time.  for the sport to grow it has to have credibility.