Jet Bikes

#1 That is the easiest way to do it, you basically just create invisible wheels. It's a bit hacky but will save you quite a bit of time and is quite a bit easier unless of course you are confident enough to code a vehicle from scratch.

#2 Take a look at the hover vehicle type. Honestly not sure if it's still in T3D, but I don't see why not.

www.garagegames.com/community/forums/viewthread/4007

#3 I'd recommend looking at the hover vehicle type as well, more specifically the Tribes 2's Grav Cycle Code:

You'll need to adjust the code to fit your models, emitters, sounds, and the Object Inheritance operator, belongs inside the Declaration. I pretty much just cut/pasted the code from my tribes 2 directory here, minus the target information (stuff not in TGE)

datablock HoverVehicleData(ScoutVehicle) : WildcatDamageProfile {
   spawnOffset = "0 0 1";
   canControl = true;
   floatingGravMag = 3.5;

   catagory = "Vehicles";
   shapeFile = "vehicle_grav_scout.dts";
   computeCRC = true;

   debrisShapeName = "vehicle_grav_scout_debris.dts";
   debris = ShapeDebris;
   renderWhenDestroyed = false;

   drag = 0.0;
   density = 0.9;

   mountPose[0] = scoutRoot;
   cameraMaxDist = 5.0;
   cameraOffset = 0.7;
   cameraLag = 0.5;
   numMountPoints = 1;
   isProtectedMountPoint[0] = true;
   explosion = VehicleExplosion;
	explosionDamage = 0.5;
	explosionRadius = 5.0;

   lightOnly = 1;

   maxDamage = 0.60;
   destroyedLevel = 0.60;

   isShielded = true;
   rechargeRate = 0.7;
   energyPerDamagePoint = 75;
   maxEnergy = 150;
   minJetEnergy = 15;
   jetEnergyDrain = 1.3;

   // Rigid Body
   mass = 400;
   bodyFriction = 0.1;
   bodyRestitution = 0.5;
   softImpactSpeed = 20;       // Play SoftImpact Sound
   hardImpactSpeed = 28;      // Play HardImpact Sound

   // Ground Impact Damage (uses DamageType::Ground)
   minImpactSpeed = 29;
   speedDamageScale = 0.010;

   // Object Impact Damage (uses DamageType::Impact)
   collDamageThresholdVel = 23;
   collDamageMultiplier   = 0.030;

   dragForce            = 25 / 45.0;
   vertFactor           = 0.0;
   floatingThrustFactor = 0.35;

   mainThrustForce    = 30;
   reverseThrustForce = 10;
   strafeThrustForce  = 8;
   turboFactor        = 1.5;

   brakingForce = 25;
   brakingActivationSpeed = 4;

   stabLenMin = 2.25;
   stabLenMax = 3.75;
   stabSpringConstant  = 30;
   stabDampingConstant = 16;

   gyroDrag = 16;
   normalForce = 30;
   restorativeForce = 20;
   steeringForce = 30;
   rollForce  = 15;
   pitchForce = 7;

   dustEmitter = VehicleLiftoffDustEmitter;
   triggerDustHeight = 2.5;
   dustHeight = 1.0;
   dustTrailEmitter = TireEmitter;
   dustTrailOffset = "0.0 -1.0 0.5";
   triggerTrailHeight = 3.6;
   dustTrailFreqMod = 15.0;

   jetSound         = ScoutSqueelSound;
   engineSound      = ScoutEngineSound;
   floatSound       = ScoutThrustSound;
   softImpactSound  = GravSoftImpactSound;
   hardImpactSound  = HardImpactSound;
   //wheelImpactSound = WheelImpactSound;

   //
   softSplashSoundVelocity = 10.0;
   mediumSplashSoundVelocity = 20.0;
   hardSplashSoundVelocity = 30.0;
   exitSplashSoundVelocity = 10.0;

   exitingWater      = VehicleExitWaterSoftSound;
   impactWaterEasy   = VehicleImpactWaterSoftSound;
   impactWaterMedium = VehicleImpactWaterSoftSound;
   impactWaterHard   = VehicleImpactWaterMediumSound;
   waterWakeSound    = VehicleWakeSoftSplashSound;

   minMountDist = 4;

   damageEmitter[0] = SmallLightDamageSmoke;
   damageEmitter[1] = SmallHeavyDamageSmoke;
   damageEmitter[2] = DamageBubbles;
   damageEmitterOffset[0] = "0.0 -1.5 0.5 ";
   damageLevelTolerance[0] = 0.3;
   damageLevelTolerance[1] = 0.7;
   numDmgEmitterAreas = 1;

   splashEmitter[0] = VehicleFoamDropletsEmitter;
   splashEmitter[1] = VehicleFoamEmitter;

   shieldImpact = VehicleShieldImpact;

   forwardJetEmitter = WildcatJetEmitter;

   checkRadius = 1.7785;
   observeParameters = "1 10 10";

   shieldEffectScale = "0.9375 1.125 0.6";
};