It looks like it was all covered. When he has the fitting they will get the size right for him. Yes, a seat elevator is wonderful. I highly recommend it.
I have a Permobile C300 series. I had them add a BIPAP tray to the back of the chair. It fits just above the wheels and is large enough to hold any BIPAP. It did make the PWC 7 inches longer though because of it's length. We place the Repironics BIPAP on the platform and use a short bungee cord to hold it in place.
BIPAP power on the PWC. I also had them add a small converter, mounted to the back of the seat. It converts the 24V of the chair to the 12V the Repironics models used. I also had to get them to order the power cord that goes from the converter and plugs into the BIPAP.
Do note that running the BIPAP all day long on the chair does run down the PWC battery. When on vacation recently and out shopping and dining for about 7 hours the power indicator on the chair had lost about 1/3 of the power. Because of this when traveling a distance of a half hour or more, I have my BIPAP plugged into the Stanley 500 amp jump starter using the Repironics Cigarette lighter adapter. The wife and I just have to remember I'm plugged in and I get ready to back out of position and leave the van. Around the house I run the BIPAP only about 2-3 hours a day so the PWC power only goes down a bar, sometimes 2. Either way with only 1/3rd power consumption the charge recharges fully in 8 hours. Yes, I plug in the PWC nightly.
So the tray and from the PWC itself make using the BIPAP easy when shopping or running around the mall. The jump starter conserves PWC battery power and also provides for additional emergency battery backup should we lose power when at home for a long period. The jump starter battery is a solid workhorse. I've run the BIPAP off of it for about 16 hours, as I recall, and it's power indicator was down to 60%