there is no harm in that either.... i had done it the same way with the (engine grounded to chasis), (batt - to chasis) and (alt + to batt +).... alot of people do it 4 way too with the additional (batt - to engine). Alot of the volt stabalizers have 5-7 grounding wires for the engine to chassis to batt -. the downside for those are that the wires are either 8 or 4 gauge.
However using a fuse is a must between the 2 + terminalslike coldie said..... better be cautious and spend a few extra hundreds then to see ur engine on fire later on.
make sure that u either solder the ring terminals (thimbles as the mechanics call them) properly to the wires or screw them tight (if the thimble have screws on them).
make sure u remove any paint from the steel panel where the wires will be grounded to the chasis.
Also if any wire is exposed inbetween the thimble and the insulation, cover it with tape. dont leave it exposed. even ofc wire's oxidise with time if left exposed to air, water and dirt.
make sure the terminals are in complete contact with the chasis or battery/alt terminals.
finally keep the wires short. dont use any excessive wire. the longer the length of the wire, the more the resistance and that you dont want.