I had a TVM rifle and loved it. However, I didn't order it and although it was a left hand lock it didn't quite have enough length of pull for me, so I traded it for a custom LH Hawken reproduction which did have the LOP I needed. The advice to spend the extra money on a swamped barrel should be heeded as the difference is very noticeable. Essentially the swamped barrel is filed thinner in the middle and gently returns to the original outside dimensions at the muzzle. It may not sound like much but it not only lightens the barrel without affecting the integrity but makes for a less nose heavy rifle that swings on to target with much less effort on your part. Also, the measurements such as length of pull, drop and cast off will be incorporated into the rifle you order. TVM does great work and I have them working on an early Virginia rifle made to my specs in .54. If you order from them you will have a wait time of at least 6 months up to a year. They are popular for a reason. However, a trip to Tip Curtis would be well worth it and if I had to do it all over again, I would have shouldered as many types of rifles as I could get my hands on. More importantly, I would not have purchased any production gun, even if it was left handed once I understood how important it is to get something that fit me, instead of me trying to fit myself to the gun. Most production guns cater to the average buyer who is of average proportions. You may find that a high end production rifle fits you well but again, there aren't any options from the factory for you to customize it and make it uniquely your own. Another thing to keep in mind is the buttplate, or lack thereof. You don't shoulder a muzzle loader as you would a modern rifle. Rather, you "hook" the curve of the butt stock onto your upper arm. This is especially true with the rifles having a very curved or crescent buttplate. If you have a physical problem, arthritis, back injury, shoulder problems then you may want to have a flat, shotgun style buttplate. That's where the advantage of having something custom built comes in. I've never owned a Tip Curtis gun but a friend has one and it is a quality piece.
I don't know what your budget it but my last bit of advice is that after you factor in the swamped barrel, get the highest grade wood that you can afford, even if it's a Southern Poor Boy. Then decide on the species of wood you like. If it's walnut then get that. If it's maple then get the highest grade you can afford and decide on the color and type of finish that you like. Show off the beauty of that wood!
Hope this helps your decision and by all means, ask more questions if you need to.
I don't know what your budget it but my last bit of advice is that after you factor in the swamped barrel, get the highest grade wood that you can afford, even if it's a Southern Poor Boy. Then decide on the species of wood you like. If it's walnut then get that. If it's maple then get the highest grade you can afford and decide on the color and type of finish that you like. Show off the beauty of that wood!
Hope this helps your decision and by all means, ask more questions if you need to.