No Bindi, the actual WEIGHT of the bipod and bayonet wouldn't make any difference in this instance because it would be the weight of the RIFLE resting on the bayonet and any bipod of sorts you choose to use. What would be the real killer is that the barrel would be 'lifted' away from its muzzle bearing and any harmonics inherent in the long tuning fork that we call the barrel would be totally lost because the barrel would be tamped at both ends.
This would be a great student project. They were always looking for these simple to replicate ideas for advanced students. Next time I'm there I'll mention it to Dr Derek Xxxxxxx. Good idea Bindi.
Bren Bipod legs...... can't you just take a set off your mates Bren? Just joking!