Hi S, I'll share my experince, hopefully this will help you or others.
First a Public Service Annoncement: 2 years ago @Dangeruss wrote an index on this thread. A+ work.
1) Presently Delkevic website is out of 42mm crush washers and have been since late summer when I tried to order a set. I've called them a few times but the phone was not answered. I also emailed a few times, again no answer. Have not reached out the them in a few months. The crush washers are available on Delkevic's eBay store for $37.99 each (not doing that). I think you'll have better luck finding 42mm crush washers on your side of the pond. Why 42mm crush washers over the stock 41mm? Note G from SF's Intro on the mega header build thread: "Significant improvement can be achieved over OEM gas flow through the exhaust port into the header primaries by using crush gaskets that do not intrude into the gas flow path when installed."
Reading @MooseMoose install thread, you can see how much the stock 41mm gaskets block the exhaust flow. To install 42mm crush washers, I used a 32mm socket to press the washers in place, my sockets slightly < 42mm OD was a good fit to insert the crush washers into the exhaust port.
A note from MooseMoose's installaion, "For some reason, TBR made their (front) pipes very narrow, and you have to somehow spread them out to get them into the ports. I mean SUPER narrow. Like, line one up with a port and the other one is only covering 1/3 of its port. I texted @sfdownhill and asked if this was normal. His response was that this was expected and that he found lining up those back pipes first and loosely slip fitting them helped to get these lined up."
After a few thousand miles and subsequent heat cycles, I removed my headers to polish them. When I reinstalled them, the front pipes were not as narrow as they were when new, this made reinstallation easier.
I did not remove the center stand for install. Just like you have to spread the front pipes for initial install, you can spread the header where it meets the center stand.
2) More info from SF's detail Intro:
-header's collector exit tube will have a 51mm od [See Note c below]
IMPORTANT - when having a slipon's midpipe expanded to fit this performance header, make certain the muffler shop expands it gradually in two or more small steps. Wade recommends drilling a relief hole at the muffler side ends of the midpipe's slots to distribute stress and reduce the possibility of tearing. Wade tested the viability of expanded slotted 304 stainless steel 18 gauge 2" od tubing by slotting a piece of 2" tubing while I was at his facility. He then expanded the slotted end of the tube in two steps to fit over the 51mm od collector exit pipe with no tearing at the slots.
I had my Staintune expanded by a shop that's both an exhaust shop (MGR Mufflers) and motorcycle repair shop (Pro J's Cycles). The technician took multiple small steps, the end result was perfect! No drilling of relief hole was necessary.
3) I also had a Power Commander / Rapid Bike dilema. Found a few old threads here on VFRD dicussing the pros and cons. I noted a few questions and called Rapid Bike. Unfotnunatly the call did not go well. I must have called Y.T. on a bad day, after a few questions, he felt I would not be a good customer, would not be able to handle the installtion and hung up on me. I was disapointed and surprised as Y.T seemed friendly on his introductory thread. Cβest la vie.
My next question: PC5 with or without a 02 sensor? I have a '99 so by default no sensor. Understaing that the autotune functionality on a PC5 is not as robust as RB I opted to go bungless header and no sensor. I know I'm not getting the optimum performance by getting perfect A/F ratios but I'm not trying to build a supreme racebike where every little HP counts. This is just a bike to cruise around SF Bay with occasional trips to the Sierras. Inititially I used a new PC5 that the nice folks at Revzilla priced matched an obscure eBay seller then gave me a promo 20%. Though first I had to update the firmware on my PC5. I ran it with the Attack map and it was crazy, power wheelies in 2nd gear! Then I torched the PC5 when my Main Fuse B fused. I was lucky and found a used PC3 on ebay for a good price. I still have the PC3 and change between the Attack map and a map for a full Erion system I downloaded from VFRD. Eventually I'll get it tuned, but it runs fine and don't have access to a bike with autotune functionality to see what I'm missing out on.
4) No bungs, no sensors, no input here.
5) In the past, vfrheaders@gmail.com is what I used to communicate with the WiLD Development Team.