I will have to go back and look at sanjays tests regarding the reflectors. I have thought I read the exact oposite, but could be wrong. If they perform better then they may well be worth the trouble of modding.
Regading "diy reflectors", the big question becomes the actual shape. I don't know if the luminarcs are engineered for the best light focus and efficiency or just made to a shape that looks nice. I would guess they are engineered. However you will find a lot of products that are just made to look nice, performance is second to looks whe it comes to sales to the average shopper. I could list thousands of items that look better than they function, and improved function would have been just as easy as improved looks.
If they (the luminarcs) are engineered with software to optimize the angles, shapes and curves of the reflector peices, then building one DIY that "is better" would be more than likely impossible. It is no different than trying DIY a venturi or other device thats shape is highly engineered to maximize efficiency. In the end you may build something that LOOKS similar but does not perform as well. Depending on the performance needed and the money saved, this may well be acceptable.
The "point" in the spiders is engineered to fit the reflector profile, adding one to a reflector of different shape is like adding a wing to the back of a Nissan Sentra. It may look nice, but does not do as much as you think it does and may in fact make things worse.
I am not trying to discount your DIY pendants, but there is a lot more to a reflector than shiny metal bent into a U shape. Most of use don't have the tools, testing equipment or skillset to design, bend and optimize a reflector that comes anywhere near an engineered commercial design.
Do DIY designs perform well enough to use? Well that is up to each individual and their setup and comfort level with regards to efficiency and output. What may be acceptable to one may be marginal at best to another.
Bean