Not all rigs are created equal. The thought process behind the PSR3 was "how do we squeeze as much rigidity out of a value oriented cockpit, without losing adjustability". 
PSR3 is blessed with the same ultra heavy duty profiles that are used on the PSR1. Significantly thicker side walls provide more mass, more weight and more rigidity than its competitors.
For the uprights, the steering section is of an overlapping design. This uses more material and costs more, but the result is a better anchor for the wheel deck to be supported by the rig perimeter.
The wheel section uses the same extremely rigid design of the PSR1. It uses a 10mm thick aluminium wheel deck, mated to profile and adjustable side plates.
PSR3 has a great pedal section. It's design is an evolution of the PSR1, where two 10mm aluminium plates sandwich two 80mm profiles, mounted with 8 direct fixings. Many drivers prefer a very stiff brake setup, and so the PSR3 had to be built with that in mind. Other designs often suffer with flex in the pedal section, primarily down to cost savings on material and design choices.
Braced Side Mount Included as standard
Continuing with the idea of "overlap = strength", the PSR3 includes a braced side mount. This reduces lateral movement when shifters or handbrakes are attached to the side mount.

To help you find the perfect height, two different mounting heights allow an 80mm level of adjustment in 1mm increments.

The side mount comes with 1 x 40x80x490mm profile, and 1 x 40x40x350mm profile.

The side mount can be attached to either the left or right of the PSR3 cockpit.
 
WIDE WHEELBASE COMPATIBILITY
The PSR3 wheel deck was built with medium strength direct drive wheelbases in mind (we think of wheelbases such as the Fanatec CSL DD (with boost kit) and Simagic Alpha Mini as being "medium strength" direct drive wheelbases).

They are extremely popular due to their blend of price, performance and strength. The PSR3 was built specifically with them in mind.

The PSR3 can also handle stronger direct driver motors such as Fanatec DD1 and DD2, Simucube 2 and so on. That being said, we highly recommend going for the PRO SIMRIG PSR1 if you are running these wheelbases at high torque settings.
Wheelbases in bold are recommended for the PSR3. Wheelbases not in bold are recommended for the PSR1.
Pre-drilled holes for bottom mounting exist for the following wheelbases:
Fanatec CSL DD / DD Pro (with optional Boost Kit)
Fanatec Clubsport DD and DD+
Fanatec DD1 / DD2
Fanatec CSW
Simagic Alpha U / Simagic Alpha / Simagic Alpha Mini
Moza R5 - requires "R5 40mm to 66mm 4 holes Adapter Plate" from Moza
Moza R9 / Moza R12 / Moza R16 / R21
All Thrustmaster / Logitech
Simucube 2 (Sport / Pro) - requires Simucube 90 degree front mount - sold separately
 
WIDE pedal COMPATIBILITY
It is common knowledge that the most consistency is gained through the brake pedal. With that in mind, the PSR3 has a pedal deck that has wide compatibility with top end pedal systems.
Compatible pedal systems using the manufacturers baseplate:
SIMAGIC P1000 / P1000i / P2000
Fanatec CSL / CSL (+LC) / V1 / V2 / V3 (+inverted)
Venym Atrax
Heusinkveld Sim Pedals Sprint / Ultimate / Ultimate+
Meca Cup1 / Evo1
BJ Steel
Asetek Forte / Invicta
Moza S-RP / CRP
SimTrecs ProPedal GT
SimCoaches P1 / SimCraft PRO / ImSim Talento 
Requires additional mounting hardware because these pedals mount from underneath. Uses 4 x corner brackets, 8 x t-slot nuts, 8 x bolts. Very easy to mount. Kit can be purchased here separately.
Thrustmaster T-LCM / T3PA / T3PM
Logitech (all)
Fanatec CSR / CSR Elite