>>In options > forms, I ajusted my maximum size form to 800 x 600 as many costumers
>>use this resolution
>>
>>Can adjust it programatically ?
>>
>>I would lilke to use large forms when programming for myself
>
>If you have a Form's base class you're always using, you can set its properties MaxHeight and MaxWidth to 600 & 800. When you would not be able to make the form bigger, I think, even in design time. I'm not 100% certain, though.

BTW, it's an interesting question - how can we control design-time properties depending on enviromental parameters? I don't know an answer from the top of my head, but this is an interesting and complex problem, I think.