if you are talking about bontrager’s race xxx lite carbon aerobar, then you’ve got it as low as it can go. this is a great bar. and it’s a valuable bar. still, it’s value is in its ability to provide a rider a tall position on a frame that’s not built to offer that tall position (relative to the rider).
example: a rider wants to ride a p3, but, he’s not sufficiently athletic; or he’s long-legged versus his torso; and this bike, while desired, has a head tube too low for the rider to adopt his optimized position without a lot of spacers, or a stem sticking up like a teenage woodrow. this bar to the rescue.
its pads sit 7.5cm above the centerline of its pursuit bar, making it the king of hi-risers (it beats a syntace c2 by 5mm).
this is why i say (ad nauseum) that bars should be treated as portable sub-assemblies. if you put this bar on, say, a cannondale slice, or a blue triad, or a specialized transition, a scott plasma, a bh crono, a valdora, well, you’re going to be up in the air. you have the opposite problem.
trek speed concepts (let’s assume you’ve got a 7-series) feature middle of the road geometries. it’s very likely that these bikes equipped with these bars will not be able to get an athletic, steep-riding, and/or long-torso’d, rider low enough.
if you were in my fit studio, i’d fit you on a fit bike, find out your optimized position, transfer your optimized saddle position over to your existing bike, then figure out what needs to happen to get the armrests where they need to be. maybe a new, really downward-pointing, stem (-25°, -30°). perhaps with a replacement, lower-profile, headset top cap (but i think speed concept 7-series bikes already come with these standard). however, it might be that the bar needs to be changed.
best to find this out before the bike leaves the shop, because, this is a very expensive aerobar, and the shop ought to be willing to absorb this back into inventory on exchange toward a different bar with lower-profile armrests. this, because this bar is, as noted, a very helpful bar in opposite cases. if this retailer carries cervelo, felt, if he’s got QR
CD0.1 bikes in inventory, guaranteed he’s going to need this bar for those customers with the opposite problem.