Insert on PM1000

[Woodworking_Hobby]

Should the insert on a table saw be slightly below the cast iron surface or flush?  I have a PM 1000 and when I level the insert plate and get the edges flush, the front ends up above the cast iron surface and the only way to keep it below is to lower the entire plate so it is below the surface. It is just the standard plate that came with the saw and was not sure if it would pay dividends to buy a better insert or a zero clearance insert?  Suggestions either way are welcome. 
 

Also, when I am squaring the blade to the surface so you reference off the cast surface?  That is how I have been checking the blade but was not 100% sure. 
 

[Chestnut]

I never bothered to try and make my stock insert flat for my PM1000. I made my own zero clearance inserts and have been using them since. For my home made inserts i try and have the leading edge of the insert a hair below the cast iron. The trailing edge I shoot for it to be a hair above the cast iron so there is little chance of a board getting stuck.

I reference the cast iron with no insert in place to get the blade square. Though i tend not to trust the squareness and usually joint all critical edges before assembly or finishing.