In addition to the simplified wire routing, I don't like fuel tank installs because of the lack of depth for a proper enclosure for the speaker. The enclosure that I use (John LeMerise's 3D-print for the Soberton 8x12mm speaker) is 6mm deep; there isn't 6mm of depth in the fuel tank (in fact, there is only about 4mm of depth there). Shallower speaker enclosures don't provide the best sound quality, and I also think that having the speaker fire down at the track muffles the high end a bit, so that the horn and bell don't have quite the same "sparkle" (you can mount the fuel tank speaker so that it is firing up into the chassis to help with this, but then wire routing becomes even harder and the depth problem remains).
There may be situations where the fuel tank is all there is for speaker mounting, but all things considered, I like to have the speakers on top of the chassis if possible.
By the way, this installation required a lot of milling of the frame to make space for the decoder, speaker and keep-alive caps, as well as a small channel on each side of the frame to route the pickup wires to the phosphor-bronze pickup strips. This is not one I'd try to do without a milling machine, given the nature of the chassis.
John C.
