Regarding Mototech undertails and visibility problems (this is for the original style Mototech with 2 round tail/brake lights): I just used a $12 universal trailer wiring converter from Wally World and wired it up a bit different than the way Mototech wants.
1) The little useless turn signal lights on the sides (that take a 194 bulb, I believe) I wired in normally - as turn sigs.
2) The 2 big round housing actually have two sockets in each: a 194 bulb and a regular dual filament 1157 (it came with a 1157 LEDs). I wired the puny 194 as a running light, & the 1157 as a stop/turn on the bright filament. Didn't use the "low" filament on the 1157's as a running light because I felt that there wasn't enough of a difference between low and high. Now, it goes from off to BRIGHT - VERY easy to notice that the brakes are on.
4) Right above the license plate, I placed a Hyperlite 16-LED module - low led as tail, bright obnoxious flashing LED as brake. No close calls in city traffic = I likey!
3) OK, regarding the trailer wire adapter: it has 5 inputs - ground, tail, brake, left turn, right turn. It then converts that into 4 outputs: ground, tail, left turn/stop, and right turn/stop. Works great!
Overall it looks VERY sleek, and I think it's actually safer overall than the factory tail/brake/turn set-up. When I hit the brakes and/or turns, latte-sipping yuppies behind me slam their brakes the fuck on in their H2's RIGHT now!