If you are contemplating raising the compression ratio on your vin and when doing so you have been told you will loose a portion of the ability of the mag to jump the gap due to a higher density air due to compression is maybe a little true but most likely you will also be increasing the lift and more importantly the duration of the cam . The normal path when all these changes are made is to raise the octane of fuel choice. So with a 40 degree spark advance possible with 100 octane , and the long duration of a racing cam which reduces the effective compression cycle . These two changes often brings the density figure at time of ignition below the figure of a stock Vin M/C.
Cheers------ Max
Cheers------ Max