Hi busterwa
I think the thing to keep in mind with landyachts is that they are sort of like permanently in high gear
In other words they dont have the ability to drag themselves through long grass or soft terrain but do have potential for high speed on hard smooth surfaces
Overcoming that initial resistance is why landyachts often push start in light winds or on soft ground The faster you go the faster you can go sort of thing

So bigger wheels are good providing they are light and have enough footprint on the ground and can withstand the side forces involved
These requirements limits the sort of wheels that are OK considerably
A lot of experimentation has been done already so looking what others have done is a good idea Longish grass will be a handicap
Hope this helps

G'day busterwa.

I've been down the exact same road as you my friend, wanting bigger wheels for paddock use. I dont have heaps of experience but I can say that reducing the mass of your craft is a big issue. Stay to 3 wheels if possible, they provide good stability and save the extra weight of steering + fourth wheel. That said, i have an idea to maybe make a yacht (oneday ) to fit onto the average vehicle track (ie: dirt road, paddock track, etc). Give it a go if your game

The permanent 'high gearing' is the real deal breaker when dealing with paddocks with grass. Just the grass brushing the rear axle as you go through it adds a lot of friction. This added to the wide footprint of ATV wheels will really affect performance. I think you would have more success finding a rougher paddock with less feed and work or using the tyres and frame (the frame in particular) to soak up vibration and undulations. Do you know what your wheels and axles weigh?

From one paddock sailer to another I wish you the best of luck.