A distance of 146.5mm does not present a problem of relevant concern.How crucial is it to have exactly 150 mm ?
The designated tube length distance of 150mm from sensor to objective shoulder will provide 10X magnification on sensor when using a 10X objective. A distance greater than or less than 150mm will have some impact on optimal magnification particularly when using finite objectives. The extent of that impact will depend on how far you deviate from the optimal tube length; but within reason it is okay to move a limited distance in either direction < or >.
Craig