why there is no hyper-parameter before Loss-focal and Loss-position when calculating Loss-instance-match? and using manhattan instead of euclidean distance?

[Running-George]

Dear authors, I have two simple questions:

1. why there is no hyper-parameter before Loss-focal and Loss-position when calculating Loss-instance-match? I believe the magnitude of loss-position is much larger than loss-focal.
2. why using manhattan instead of euclidean distance? it seems to me it is more proper to use euclidean Thanks George