Your saw is almost identical to my SIP which I modified to a quick change by using an indexing lever of the appropriate size as here.
http://www.wdsltd.co.uk/products/Machin ... ert--1607/
Also take off the clamp and clean off any roughness left on the underside from when the slot was machined, I used a needle file.
Run some abrasive paper through the slot to clean out any swarf or lubricant left by machining.
When you put the blade in the clamp keep it as close to the front as possible and the lever only needs to be finger tight
HTH