Interesting. Do you have any pictures of the differences in material thickness or seam welding? If so I would love to see that.From the sound of it, you've already decided in your mind that the HF isn't lighter or whatever it is you have decided, its not super clear, so I'm not sure you will believe anything I have to say at this point, but here goes.
20+ years of working on these cars, taking them apart, cutting them apart, seeing them wrecked, putting them back together. Both race cars and plain stock style street cars. Seam welding too many of them to count. Researching. Seeing what others have done. The measured weight of their cars, (not the wikipedia weight that you quoted but actual weight), material removed, and comparing that to a stock HF car. That's where I got my info from. Tons of research and my own experience. The HF is a much lighter car, specifically the 88-89 variety. Most are in the 1800 lb range or less When seam welding a chassis, it's fairly obvious that the HF requires more to equal the Si.
My problem here is you keep mixing up different things. You keep talking about bolt ons like they are the unibody, you have compared 89Hf to 89Si like they are not VERY different. All the 88 cars were significantly lighter, and the only 89 cars to use the lighter body style were the HF, which you obviously know and are using to skew the comparison. Why wouldn't you compare an 88 Hf to an 88 Si? Or a 90-91 HF to a 90-91 Si? Or better yet an Hf to a DX since neither of those have the sunroof body of the Si that was obviously a different shell?I'm thinking that you are assuming all CRX's went down the same assembly line and some were dubbed HF and others were dubbed Si, and then received the appropriate add ons, much like an American assembly line works, but that wasn't the case exactly for the CRX. The HF is a different animal. Different and smaller dash bracing in 88-89, the list goes on and on, and literally almost everything is different (brake booster, front brakes, struts, etc.). Including the actual thickness of the metal in the shell itself.
I am not saying you are wrong, as honestly I have never seen any proof of what you are saying one way or another, but your comparisons and arguments are highly disingenuous.