Hi,
after seeing the problems of MM with two of his customers, I want to give my humble opinion as a builder.
With my years of experience, I think both sides have made mistakes ( I have also made some, but since I work like I explain you at following, everything went well ).
1st. A handmade build like these, never takes the same time. One thing makes a job day, in another build, can lead 3. Solution, if the estimated construction time is 3 months, adding 50% to the contract, ie give the delivery time of 4 ½ months, so you can work in peace, if a problem occurs, you have time to fix it and normally deliver the car before the end date, so that the customer is always happy give it two weeks before, than only one day late .....
2nd. Before you start, the contract is written in all that the customer want, to the last detail, so nobody has to remember .... is written and is to be met by both parties. If something changes, add in the contract with the date of the change, costs, etc...
3rd. A car made of fiberglass, if you wish without waves, you have to put filler, high or low depends on the kit, but if you work with the finest materials and time to prepare correctly (Part 1 ...), contract must not break ever, at least we use ourselves, it is difficult to sand (it's our problem, not our customers), but never breaks ... for something costs 790 USD 4 gal.
4th. In the other case, a perfect job is not seen, ie they work the best we can from within, into parts that never see, and the iron of the sub-chassis is oxidized quickly, but only superficial. How can avoid this?, Protecting immediately after installation. If the car is not finished, you cant tell, " the builder dont do this or that....".
5th. Have confidence with your builder, the builder have confidence with the final payment of the customer be done. During the process may have complications or problems that frighten a client who does not know how it will work, but you have to have confidence in the outcome, for that we have a contract, and if in the end, or during the year guarantee, does anything is as we agreed, is in the contract and the builder is required to repair / rebuild, by hook or by law. Visit frequently your builder, and if something is not like you wish, tell him, maybe has a reason or can be changed...
Many times, other builders speak ill of the work being done by others, to try to take that job, do not be fooled and leave work to someone who has demonstrated his ability. And for the constructor, be honest and always working as if the car was for you, listen to your customer as if you are the customer, and never give personal excuses, is a job for money, not a hobby to help a friend, by a very good relationship with. Do not promise things with a fixed date if not 100% sure you can fulfill, because if you fail to your customer, lose their confidence.
ALLWAYS return back his calls / e-mails. The worst is dont know what is happening.
A good job, delivered on the date it is always a happy customer ... sometimes customers are difficult, when at first everything was cordial, if everything is clear and in writing before you start, problems will always be very few or none.
I think everybody has a part of reason, always a bad agreement is better than a good lawsuit, try to fix before getting angry, perhaps it is easier to solve than it seems...
With my best wishes for all in this new year.
I hope you can understand my poor english....

Amén.
Better impossible.