I think that the weldpak 100 is a little small are you using gas? you might be surprised at rhe difference that wire size makes on the 110 machines...
I had a 100 in my pit kart ran off 6500 watt generator with .023 and .030 wire you had to take your time but it would do 1/4" buy they're duty cycle sux...weld for 2 minutes wait 8 minutes till it cooled down enouph for the arc to get stable...weld for 2..
Now if your using flux core wire..... :-[
Get the kit and try gas...the kit will transfer to the 180 if you need to go up in size...
Or toss it in the back of the wagon...and bring it up...my 251 is just collecting dust