Thanks for the input but that doesn't really answer my questions.
How much lift is safe without destroying shafts? Does anyone have the same wheeler with a lift who can chime in?
First off I have no idea about your ATV as to what is CV safe or unsafe concerning amount of lift. Far less information or experience will be found on a 98 300 and even less chance of finding a 98 300 that someone has lifted. Can we say RARE? Are there venders that even offer lift kits for 98 300's? So I can offer only generalities. Any time you increase the working angle of a CV joint the chance of breaking that CV joint increases proportionally. Doesn't that 300 have a solid straight rear axle with No CV joints? Adding a lift kit does not increase the clearance between the ground and the rear differential. Only a larger tire diameters will give you more clearance in that case.
Therefore a 2" inch lift is less strong then Stock or no lift and a 4 to 6 inch or more lift is getting dangerous in my opinion with the CV angles. That is physics and the nature of CV joints. The greater of angle the more prone to breakage with stress. Keep in mind your 300cc engine has less power then a larger machine so your chance of breaking a axle would be far less then I would experience with my 650H1 or 1000H2 with equal lift. You may be able to lift it up real high and have no problems at all?
In practice it seems a 2" or maybe even 4" of lift is nearly as strong as no lift. It all depends upon the thumb. There are a lot of guys running 2",4",6" lift and experience no real problems with axles with good thumb control. More than 6" or sometimes even with 4" to 6" the axle at the hub may require shims or an longer axle to keep the axle seated in the differential.
Then there are those who can destroy an axle on a stock non lifted machine with poor thumb management. How much is safe depends upon your thumb more then the lift when it comes down to it. There is also the option of using stronger axles too though. There is no clear answer really.
A lot depends on where you ride also. More lift means higher center of gravity and a higher center of gravity means it will tip over to the side easier. For me, Riding in the Rocky Mountains a higher center of gravity is more dangerous so I would not consider a lift at all.