Thought I would share my latest updates to my mod. I was one of the ones that reported that my maxijet stopped working well but still worked fine if I hooked it back up as I origionally had it. Turns out that my propeller/acrylic tube piece that connected to the maxi-jet magnetic cylinder was slipping and thus not producing the desired flow. So it was not the maxi-jet that was failing, it was my modifications that was failing.
So here are my 3 main modifications.
1. BullDZR idea of using the pvc knockout (test) cap was a wonderful idea. The 1 1/2" pipe is close to the right size to connect to the maxi-jet but still allows for slippage and vibration. I just took the pvc knockout cap and put it inside of some 1 1/2" pvc and used acrylic glue to glue it in place. WORKS LIKE A CHARM. The fit on the maxi-jet is VERY tight. Tight enough that I doubt you would even have to use the maxi-jets clip things to hold the pipe on the maxi-jet motor.
2. My second problem with my last mod was with the end piece of the 1 1/2" guard that holds the titanium shaft in place. I originally used a pvc cap for this and tried cutting a hole in the center of the cap to hold the shaft. This didn't work out so well for me because it was hard to get to and wasn't very centered. So this time I tried to make something that looked similar to what bassman57 posted above. I had no way to make one of those and so I improvised. I ended up taking a 1/4" acylic sheet and a 1 1/2" hole saw and using a drill press I was able to cut out an acrylic disc that fit almost perfectly in the 1 1/2" pipe. Another bonus is that with the hole saw it has a drill bit in the center so I have a perfectly centered hole in the disc. After I had the disc I then basically cut/grinded/dirlled it until it looked like bassman57's picutre above except without the outer ring. (Note: as I was cutting/grinding/drilling I planned to have pieces of the disc touch the outer pipe thus you must not do any cutting grinding or drilling in these areas. For example with bassman57's picture above, the outer ring would represent the pipe and the center region represents the disc. You dont want to alter the disc where it meets the pipe.) This front guard/disc fit perfectly in the 1 1/2" pipe and all I had to do now is put it in the end of the pipe and use acrylic glue to set it in place.
3. This my final part of my new mod. My last problem I had with my mod was with attaching my propeller on the acrylic tube to the the magnetic maxijet cylinder without making it perminant and also not allowing it to slip. What I found out was when you heat up the acrylic tube it stretches quite easily. So I put both the acrylic tube (with propeller) and the magnetic cylinder on the titanium shaft, then (while on the titanium rod) I rotated the end of the acrylic tube over a candle for a few seconds and then pushed the magnetic cylinder and the acrylic tube togeather. What this does is it heats up the acrylic tube so it is flexible and then when you push them togeather it forces the acrylic tube over the end of the magnetic cylinder. Then to tighten the hold of the acrylic tube I then rotated it over the candle again which caused the tube to shrink tightly over the magnetic cylinder after which I dipped it in water to cool it quickly. If you remember the magnetic cylindar has a plastic notch which is used to attach the normal maxijet propellar to the cylindar. This notch now acts as a catch and the tube(with propellar) is now connected to the cylinder and it doesn't slip. The reason you must do all of this step using the center titanium rod so that the connection is straight so that it will spin well.
Sorry I don't have pictures. If you need some I would be more than willing to get some, or if you need clarification let me know.