TRF201 chassis is bottoming or "slapping" the ground when landing,

[guinness]

my chassis is slapping the ground when landing,
i use
oil Schumacher 35 all around
blue AE springs front kit piston (4mm spacer inside shock)
grey AE springs rear kit piston
21mm ride high all around
front shock position SECOND FROM TOP ON TOP TOWER , MIDDLE ON HARMS
rear shock position THIRD FROM TOP ON TOP TOWER , MIDDLE ON HARMS

any particular way to build shocks?
any help appreciate.
thanx