Jus' for some "stability" clarity, a 'Schwinn Meridian' is an upright delta tricycle & it's true this is one of the least stable configurations at speed... there are however other trike designs that while there are other considerations to be concerned with, (price, ease of build, mount/dismount, visibility, etc) turn & bump stability is less, even far less a worry.
Tadpole trikes (two in front) haven't nearly the propensity for tip-overs, even less so if it's a recumbent & even deltas can be very stable as a long wheelbase recumbent. Recumbents can be difficult to motorize, expensive, even awkward if the rider has some physical disability - but their stability is far
greater due to their low center of mass. Tadpoles are far more stable until they're suddenly not whereas deltas are just somewhat unstable regardless - for example taddys are great, unless you start to sideways... then bad things happen very quickly lol, whereas they use (low) deltas for drifting.
Bumps/bump steer is a concern with all trikes, less so with what few have a suspension - but is a difficulty inherent in their design as when one side's wheel leaves the ground that leaves the other two in-line (center & side), but not the direction you're directly facing, so it becomes a bicycle in a turn rather then the tricycle you thought was going straight. Regardless of upright or recumbent generally taddys have more an issue with bumps & steering then deltas, but wheelbase also plays a factor, as does shocks & dampeners, if yer into that sort of thing.
If you wish a trike there's a bunch to choose from, it all depends on your needs & wants - if there are none other then stability at speed, a recumbent taddy is a good bet. Ease of build & budget? An upright delta like the Schwinn is a great way to get'er done. Dare to be a lil different? Recumbent deltas are fast & fun...
Your call, I jus' wanted to say not all trikes are so risky, that speed & stability are both comparative - that while all the previous advice is mostly accurate & defo well-intended, there are some oversights regarding additional suggestions, some amount of over-statement in concern for your well being... and I'm not entirely sure I'd agree an actual 4hp has such limitations.
Uprights reach 30+mph fairly easily with little more then 1.8-2.5hp with number of wheels notwithstanding, the additional drag minute comparatively. My recumbent taddy (far too) easily exceeds that with but a mere 2.5hp, but it has a low profile (wind resistance), multiple gears & a four stroke's torque
Food fer thought anyway
edit: ...I knew I had it somewhere lol, here ya go map - a neighbor's upright delta Harley & my recumbent tadpole, his is defo faster w/the oodles of engine (also cooler & worth far more ofc) but w/o a doubt mine is more stable in the hairpin turns at least... gotta take what win ya can I figure heh;