I would also follow Scott's logic as well. You should drop Jason a note to get a clarification if it will effect the car you will buy. He is the Performance Solo director this year.
The question intrigued me, so I went digging. Seems SCCA has changed their mind on this from 2013 to 2014.
The 2014 SCCA Performance Driving Experience rules say this:
http://www.scca.com/assets/2014_PDX_CT%20Driver_Rules_final.pdfELIGIBILITY OF VEHICLES: All vehicles must provide factory original (or better) seats that
are securely mounted, seatbelts (SFI or FIA rated are recommended), and roll over protection for
both driver and in‐car instructor (if used).
Hardtop and Targa top vehicles are allowable.
Convertible vehicles operating with the factory roll over protection system are allowable.
Other convertibles should have either a factory hardtop or a 4 point roll bar. If a roll bar is
used, it should meet the roll bar requirements found in the TT/HC Driver Information TTR.
Vehicles that are in compliance with road race, solo, rally or time trial rules are allowable.
Drivers of open top vehicles should use arm restraints or run with the top up.
The 2013 Rules were different and more complicated:
11.1. PDX (LEVEL 1)
At PDX (Level 1) events, any car that is street legal will NOT require a roll bar/roll cage, except for Convertibles and Targa* top automobiles. These cars must have either a roll bar meeting the requirements of section 11 of the TTR, a factory roll bar/roll over protection , or a factory hard top using the factory mounting hardware and mounting points. Owners of cars equipped with factory roll bars/roll over protection must present documentation stating that the device is a roll bar or roll over protection at the time of vehicle tech inspection (a factory issued Owner’s or Shop Manual will fulfill this requirement.) Targa* top (and T-top) automobiles may forgo the roll bar requirement under the condition that the Targa bar meets the height requirements set forth in 11.1.1.B. For the purposes of this determination only, street legal will be defined as a car which meets local requirements for inspection (if applicable) and the car in question must possess CURRENT, VALID registration. If this street legal requirement is not met, then the roll bar requirement as stated in this section shall apply.
*Targa top, targa for short, is a semi-convertible car body style with a removable roof section and a full width fixed B-pillar and roof section. The rear window can be fixed or removable.
11.1.1. Basic Design Considerations
The basic purpose of the roll bar is to protect the driver in case the vehicle rolls over or runs into an obstacle such as a guardrail or catch fence. This purpose should not be forgotten.
The top of the roll bar shall not be below the top of the driver’s helmet when the driver is in normal driving position, and shall not be more than six inches behind the driver. It is strongly suggested that the roll bar extend at least three inches above the driver’s helmet. In case of two driver cars, both drivers must be within the roll bar height requirement, however only one driver must be within six inches of the roll bar. In a closed car equipped with a roll bar/cage, it must be as close as possible to the interior top of the car.
I throw these out as they are often what the ASN National Solo Committee will use as guidance when issuing Cdn rulesets.
Brent