Boot top sewing machines

[pogue44]

Greetings, 

Some questions about boot top sewing machines.  Obviously the go to machine for decades has been the Singer 31-15.  No question about it's fame and usefulness. 

But I recently saw the Cobra 5550 BB and had a chance to test one.  Fine machine.  Big bobbin.  Roller foot.

I have a juki 555 knock off machine head already stashed in a corner of my shop I bought somewhere for less than $100.

If I decided to convert this machine would I, could I....etc.....I have seen a few roller foot conversion videos.  Specifically would I have to change the feed dogs?  Also can you convert a regular bobbin size to a M type bobbin size?  I can see where the large bobbin would come in handy for this use.

Finally, it seems like the 555 models would be a bit light weight to do boot tops if you go through the lining and the outer layer from the comments I have seen.  The Cobra model has the servo and speed reducer. I'm guessing this set up with the right needle size gives the machine enough power to get the job done.  I have both a servo and reducer in the shop also so I could optimize with a similar set up.  I just don't want to go through the trouble if it's not going to work out.  So any input is appreciated.

Any other machines or set ups that would work good, better, best for boot tops?  Hard to improve on a gabazillion years of tradition with the 31-15.  But major props to Cobra for doing something different.  The Cobra machine I tested was awesome and if I didn't hoard old machines it would be a great investment I think.

Thanks for any advice.