hello mate
unfortunatley yes you do need to remove the tie down rings as they go through the tub floor to the chassis,
just done mine today and its a pain in the a**e the roll rins are a pig to get out i got a bar through the ring to stop it spinning, lots of wd40 and just hit them hard with a small but heavy hammer to move them to start with then a 80mm m8 bolt is about the right size to give enough room to swing a hammer but long enough to keep fingers away,
centre front and both rear corners are more awkward as there is stuff in way
tub is not as heavy as you would imagine wish i did it earlier as everything is so accsable
think i may use nut and bolt when it goes back on
good luck
mark