I had lots of issues with the Detweiler. The first of them being that they advertise their plate as an 8", when it really was a 7 1/4". Closer to a 7" plate to me, and I told them that. The second issue I had with it was that I couldn't bring my engine all the way up. They ended up selling me an "extention plate" that was totally useless. I couldn't get to any of the controls I needed to get to with that solid plate in the way (other brands use two pieces - one on each side). This is what ended up happening when I tried to bring my engine all the way up (notice the hydraulic line fittings banging against the jack plate):
When I called them back, they insisted that they had told me to install it between the transom and the jackplate. Well... that didn't work. It wasn't designed to be put there, and looked like it was about to crack my fiberglass in several places when I started cranking it down. It has "fingers" all over the place instead of being flat on the edges, and those edges were digging into the fiberglass. In the end, the guy on the phone kind of got really short with me and asked me "Well, what do you want me to do?" I responded that I wanted him to send me an actual 8" plate that I could use. He said "Well, we don't make an "actual" 8" plate. When I told him they shouldn't advertise it as an 8" if it isn't actually an 8", he got a little more annoyed and asked me again "Well, what do you want?" I then asked for my money back, and he agreed - less the "restocking fee".
I got on the phone and called Bobs Machine shop and explained my delima. They sold me the plate that day, and shipped it VERY quickly. If I'm not mistaken, I think they overnighted it to me, as they knew my engine was hanging on a engine hoist after removing the Detweiler plate. We went back and forth over whether to do 8" or 10", but ended up going with the 10". It came in, and was everything I wanted it to be. Quality manufacturing... and actually 10" when I measured it. Customer service was awesome - much more friendly and helpful than my experience with Detweiller.
As far as the gauges - Get Bobs LED gauge. It's dead on accurate. It displays LED's in 1/4" inch increments. I've had a few different brand gauges, including some higher dollar ones, and nobody beats the accuracy of this gauge. I like to keep my engine at 3 1/4" on the gauge most of the time, and only make minor adjustments as needed. You won't (or shouldn't) be messing with the hydraulic plate all that often, unless your water conditions change constantly. I tried adjusting up and down for better holeshot and then bringing it back to 3 1/4" for my run - I've discovered that most of the time it's better just to leave it on my mark through the whole run. I might bring up the engine for shallow water, or down for a rough water run, but other than that, it stays on my premium running number. (Your number may vary - you need to figure out where your boat runs best after you install it).
No, Sorry about that - I'm not telling you to go with a 8" over a 6". Sorry if I confused you on that one. I was saying that a Triton TR-20X with a 225 likes a 8" or greater setback. 6" is the normal starting point for most boats that I've set up, and the great thing about a 6" is that you can add low cost 2" Bobs Machine Shop spacers and turn it into an 8" immediately. You can't go the other way that easily. You would have to buy all new sideplates to bring the size down to a 6" from an 8", and that is considerably more money. A 6" plate is normally sufficient for most rigs.
Here is my original TH Marine plate that came with my boat, along with the 2" Bobs Machine spacers I added. The additional 2" of setback made all the difference in handling on my particular rig. Again - your results may vary.
All the best,
Glenn