if to thick of gasket makes the squish to big so i look into a bigger dome maybe a 20cc
Unfortunately there is a lot more to cylinder head design than selecting a head volume and setting the squish clearance to this weeks most popular number found on the internet. Squish clearance and head volume are very popular topics on almost every forum. I have not read any threads in any of the public forums where the authors seem to have a very deep understanding of what they are writing about when it comes to the above mentioned topics.
When we use a cool head I just order a blank dome and then machine our own combustion chamber shape on it. It is very difficult for me to try to answer questions on the subject without having listeners that are also engineers.
Lowering the compression ratio raises the exhaust temperature and will usually make the engine rev a little higher. Lowering the compression ratio has a similar effect to the power curve as does shortening the exhaust pipe. Raising the compression ratio lowers the exhaust temperature and has a similar effect on the power band as making the exhaust pipe longer. (More low end at the expense of moving the power peak to a lower RPM.)
A chrome pipe should turn blue for the first foot or so. Lowering the compression ratio will add a little more blue to your pipe. How far the pipe turns the chrome blue depends upon the exhaust temperature, the RPM and how long the throttle is wide open at any given period.