To do that you have to look at the code which may or may not be available to you if you grab something from the web.
Another way to check is once you have the picture converted at PostImage, just open it in any program you want to and see how big it is then adjust it before you put it into the thread.
Look at the options you have at PostImage
There are links for thumbnails for forums, thumbnails for websites etc. See which one is best suited for threads and just use that link all the time.
The problem is that my brain is actually very, very limited. I mean, VERY.
Write poetry? Play musical instruments and learn how myself? Cook from scratch? Draw? Make my own herb formulas? I can do all those.
But the things you describe above... can’t do. I can only do very, very simple, primitive stuff with computers.
I do appreciate your help and I’m sure most freepers would totally grok it and be able to follow them. The only stuff I can do is copy and paste bits of html that people give me. I’m amazed I can even do that.
You can do it, it just takes a little practice.
Grab an image you have already posted in here and just change the size and post it til you get it right.
YOU CAN DO THIS, I know you can!! :-)