Best way to mount a scope rail

I’m on planning stages of converting my .357 Evanix to a bullpup. However, I’m undecided of what methodology to use for scope rail mounting. Options as I see them:

a) Mount the rail to the barrel. This would make the rail unaffected by the air tube expansion. However, it will affect barrel harmonics. 18mm barrel has not that much wibes but it may affect accuracy.

b) Mount the rail to the airtube. This would leave the barrel free to vibrate with it’s band as restricting factor but air tube movement as air volume rdeuces may again affect accuracy or POI.

c) Mount the rail to the breech on one end and airtube on the other. This leaves barrel free to vibrate while potentially reducing the airtube expansion effect. ALternatively it may make the airtube expansion effect worse as the other end is fixed and the other moves. I have two bullpups using this principle and they are rather accurate.

d) Mount it on both airtube and barrel. This would probably be the worst of both worlds

e) Some other way of mounting it?

I’d like to hear your opinions and thoughts of what’s the best way of doing the scope rail.