Shower and Sink to Gray Water and P-Trap Questions?

Figured I'd ask.. I don't see any recent posts addressing this on here..
I am doing a shower install on my CC project and want to drop the drain thru the floor of the trailer, then do the 'P-Trap' which would be 2" of course, and come back up and over then into the 'Gray water' holding tank.. I don't want to elevate the shower stall at all.. I have a brand new 3/4" floor to put a hole thru..
I also planned on doing a sink 2" p-trap under the sink per norm.. then just tying the 2 lines together under the trailer just before the 'Gray water' tank so I only need 1x hole put into the holding tank..
How much clearance would I need above the holding tank to get this worked out?? anyone got dimensions on a 2" P trap?? and/or should I use the 'low-profile' P-trap if there is such a thing and if so would it matter much on this idea as I still need to come in either high on the side or on top of the holding tank..
I figure 2" PVC or ABS is the same OD of 2 3/8".. so I need at least that and then what about the 90' elbow down?? and how long is the 90' elbow 'spigot' length..
Anyone got REAL pictures of this type of setup on there rigs??
I am doing a shower install on my CC project and want to drop the drain thru the floor of the trailer, then do the 'P-Trap' which would be 2" of course, and come back up and over then into the 'Gray water' holding tank.. I don't want to elevate the shower stall at all.. I have a brand new 3/4" floor to put a hole thru..
I also planned on doing a sink 2" p-trap under the sink per norm.. then just tying the 2 lines together under the trailer just before the 'Gray water' tank so I only need 1x hole put into the holding tank..
How much clearance would I need above the holding tank to get this worked out?? anyone got dimensions on a 2" P trap?? and/or should I use the 'low-profile' P-trap if there is such a thing and if so would it matter much on this idea as I still need to come in either high on the side or on top of the holding tank..
I figure 2" PVC or ABS is the same OD of 2 3/8".. so I need at least that and then what about the 90' elbow down?? and how long is the 90' elbow 'spigot' length..
Anyone got REAL pictures of this type of setup on there rigs??