in my opinion ... comex volume has been decent on these
since going electronic on globex .. plus their fees are slightly lower than ecbot at this time
check with your broker on commissions for ecbot vs comex
another idea ... you can scale in using the mini contracts
on ecbot ( i.e. YG + YI ) just be careful on the prices you pay
on the mini silver ... there is more slippage in general trading silver ... esp in mini
another option could be to have a long short in the ETF's
( i.e. GLD + SLV )
different tax treatment though and sometimes the ETF's
are hard to borrow