its simple........this has been a problem for ages and dissected and cured on this forum many times.......torque to 18lbft pounds......dyno in the normal way, re-torque when hot on the dyno.......let the engine cool down till cold.....re-torque again.......job done, they will not fall out.
The problem is the gasket experiences what is termed as "compression-set" whereby it relaxes after the first heat cycle, the net result is the side cover bolts then loosen off, I see it loads in the UK from established engine builders who should know better, it wrecks a track and dumps oil everywhere........using some blue Loctite 243 during the process above adds another level of security.