The "standard" control lock for a PA38 (and PA28) is to loop a seat belt through a control yoke. I've an idea that this is even mentioned in the tomahawk POH but I'm not absolutely sure.
I've also seen people using the seat back pushed forward against the yolk and the yolk trimmed against it. My club stopped doing that due to various seat trim breakages when it's done carelessly - the internal trim in a tomahawk is particularly fragile.
Nowadays my club secures the elevator by trimming forward all the way and doesnt' bother to secure the ailerons. I don't know why - I much prefer the "standard" seat belt loop method where everything is secure - but I do what the boss says anyway.
I don't know about the dip-stick. Most (all?) PA38 operators I know work out the fuel load by looking through the filler hole and siting the fuel level against the large 'X' which is clearly visible on the fuel tank back wall. This is much, much easier to do on a tomahawk than on, say, a high wing Cessna single.
Does that help?