After putting over 500 miles on my GTM I have some thoughts on the Mendeola SDR5 that may help some in the future. I have the 4.11 geared one. I bought this car finished, but if I were to build one I would definitely go with the 3.55 final drive gear. The 4.11 in my opinion is too much for highway driving. I drive the car mostly on the turnpike, 80 MPH is average speed for me, and believe me in South Florida at that speed there will be quite a bit of people passing you by even though the speed limit is 65 MPH. At 80 MPH the tach is at 2,800 RPM's with 335/30/18 tires. That is way too much for comfortable driving. At 90 MPH you are easily over 3,200 RPM. Noise is high and gas mileage (if that matters to anyone) is in Cuda Hemi territory. At 60 MPH you are a little over 2,000 RPM.
If you just drive around town, this is a race car, or you just do not plan on driving it much then sure buy the 4.11 geared tranny. If you actually plan to really use the car, it seems like 4.11 is too much especially for highway driving. The transmission seems to work fine, but the shifter action sucks. This car has the FFR billet shifter (which some seem to not like very much) and cables. Transmission goes into all gears, with what seems to me to be a too much force.
You take the car out put it in first gear, and if you do not think about it, it will go fairly easily (although with a little much effort IMHO) into 2nd, 3rd, 4th and 5th. Now after you are on the highway lets say you want to downshift to 4th, haha good luck finding it... 3rd almost as difficult but you may get lucky. To go into 4th at highway speed, I pull the shifter all the way as if I was going to go into 2nd and start pulling it into 2nd without actually going into the gear, that gets me "into the gate", I then just push it out of the gate and find the gate next to it (which is 4th) and pull it in. Most modern shifters if you put the car in neutral and pull straight down, you get into 4th gear and straight up you get into 3rd gear. On this shifter the 3rd and 4th are not like that, if you are in neutral, both 3rd and 4th are offset to the driver when in neutral. 1st and 3rd and 2nd and 4th are very close together on the shifter. At some point I will try to see if I can adjust the cables better, but I do not think that will make a huge difference. I have no idea if there is any adjustment on the shifter, will be looking into that...