Basically, SCCA PDX and NASA HPDE allow factory seat belts, with or without roll bars.
However, when one uses a harness, the competition rules apply.
I couldn't find anything that specifically addresses belt pass-thrus.
SCCA Performance Driving Experience (HPDE)
Time Trials level 1 (PDX)
10.8. REQUIRED DRIVER SAFETY EQUIPMENT
... Please note that for PDX (Level 1) events, the following guidelines apply for restraint systems - All cars that are required to install roll bars must comply with Section 12 of the TTR. Cars that choose to install a roll bar may use stock restraint systems, provided that the roll bar does not interfere
with the function of the system in any way. For these cars, there is no age limit on harnesses so long as the harnesses are in visibly and physically good condition (i.e. no fraying, damage, or excessive discoloration).
Cars that do not incorporate roll bars or cages may use the stock restraint system in its entirety, or use a restraint system that complies with TTR [time trial regs] Section 12.
SECTION 12. – DRIVER RESTRAINT REQUIREMENTS
All drivers in PDX (Level 1) events may utilize a restraint harness meeting the specifications of section 12.1 in lieu of the factory/OEM restraints.
12.1.
1. A four point restraint system, for use in enclosed automobiles only, may be employed where the driver is seated in an upright position. Only 4 point restraints that incorporate a manufacturer designed method for prevention of submarining may be used. Five, six or seven-point systems are highly recommended in all cars including automobiles where the driver is seated in an upright position.
4. The single anti submarine strap of a five point system shall be attached to the floor structure and have a metal to metal connection with the single release common to the seat belt and shoulder harness.
5. The double leg straps of the six point or seven-point system may be attached to the floor as above for the five point system or be attached
to the seat belt so that the driver sits on them, passing them up between his or her legs and attaching either to the single release common to the seat belt and shoulder harness or attaching to the shoulder harness straps. It is also permissible for the leg straps to be secured at a point common to the seat belt attachment to the structure, passing under the driver and up between his or her legs to the seat belt release or shoulder harness straps. All straps shall be free to run through intermediate loops or clamps/buckles.
NASA HPDE rules:
11.4.8 Seatbelts and Harnesses
"The seatbelts should be in good condition. No damage may be present on the seatbelts and they must be the factory configuration. Any harness or any restraint system, other than factory stock, shall conform to CCR section #15.5, in all respects* except for the expiration regulations. Harnesses that are expired for racing may be used providing that they are in at least very good condition. The use of a lap belt without any shoulder
restraint is not permitted. Passenger seatbelts must meet the same minimum
requirements per the CCR as the driver seatbelts if being used by a passenger.
Note: passenger equipment need not match the installed equipment on the driver’s side.
*Aftermarket DOT-certified belt sets, installed to the manufacturer’s specifications may be allowed. Proof of DOT certification and proper installation is the driver’s responsibility.
15.5 Driver restraint system
1. All vehicles must have a five (5), six (6), or seven (7) point seat belt system.
2. A five (5) point system consists of: a three (3) inch lap belt, two shoulder belts that are either two (2) or three (3) inches wide, and a two (2) inch anti-submarine strap.
3. A six (6) point system is recommended for cars where the driver is seated in an upright (to thirty (30) degrees) or a semi-reclining position. It consists of two (2) anti-submarine belts in addition to lap and shoulder belts. Note: Current FIA Approved belt sets with two (2) inch lap belts are acceptable with the six (6) point system.
