Rules are copied and pasted below. No two seat limit, however if you do not hold a class 1 or 2 medical you are restricted to only one passenger.
61.460 Privileges of recreational pilot licences
Subject to Subpart 61.E and regulations 61.465 and 61.470, the holder of a recreational pilot licence is authorised to pilot a single‑engine aircraft as pilot in command or co‑pilot if:
(a) the aircraft is certificated for single‑pilot operation; and
(b) the aircraft has a maximum certificated take‑off weight of not more than 1 500 kg; and
(c) the aircraft is not rocket‑powered or turbine‑powered; and
(d) the flight is conducted by day under the VFR; and
(e) either:
(i) the aircraft is engaged in a private operation; or
(ii) the holder is receiving flight training.
61.465 Limitations on exercise of privileges of recreational pilot licences—general
(1) The holder of a recreational pilot licence is authorised to pilot an aircraft in a Contracting State’s airspace only if the holder has the permission (however described) of the Contracting State to do so.
(2) The holder of a recreational pilot licence is authorised to pilot an aircraft carrying more than one passenger only if the holder:
(a) also holds a current class 1 or 2 medical certificate; or
(b) is accompanied by another pilot who:
(i) holds a current class 1 or 2 medical certificate; and
(ii) occupies a flight control seat in the aircraft; and
(iii) is authorised to pilot the aircraft.
(3) The holder of a recreational pilot licence is authorised to pilot an aircraft above 10 000 ft above mean sea level only if the holder:
(a) also holds a current class 1 or 2 medical certificate; or
(b) is accompanied by another pilot who:
(i) holds a current class 1 or 2 medical certificate; and
(ii) occupies a flight control seat in the aircraft; and
(iii) is authorised to pilot the aircraft.
61.470 Limitations on exercise of privileges of recreational pilot licences—endorsements
(1) The holder of a recreational pilot licence is authorised to pilot an aircraft outside the following areas only if the holder also holds a recreational navigation endorsement:
(a) the area within 25 nautical miles of the departure aerodrome;
(b) a flight training area;
(c) the area that is a direct route between the departure aerodrome and a flight training area.
(2) The holder of a recreational pilot licence is authorised to pilot an aircraft in controlled airspace only if the holder also holds a controlled airspace endorsement.
(3) The holder of a recreational pilot licence is authorised to pilot an aircraft at a controlled aerodrome only if the holder also holds a controlled aerodrome endorsement.